Stanford Research Systems SIM983 Operation And Service Manual

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Operation and Service Manual

Stanford Research Systems

Scaling Ampliﬁer

SIM983

Revision 2.2 • August 28, 2006

Certiﬁcation

Stanford Research Systems certiﬁes that this product met its published speciﬁcations at the time of shipment.

Warranty

This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment.

Service

For warranty service or repair, this product must be returned to a Stanford Research Systems authorized service facility. Contact Stanford Research Systems or an authorized representative before returning this product for repair.

Information in this document is subject to change without notice.

Stanford Research Systems, Inc. 1290–D Reamwood Avenue Sunnyvale, CA 94089 USA Phone: (408) 744-9040 • Fax: (408) 744-9049

www.thinkSRS.com • e-mail: info@thinkSRS.com

Printed in U.S.A. Document number 9-01598-903

SIM983 Scaling Ampliﬁer

Contents

General Information iii

Safety and Preparation for Use . . . . . . . . . . . . . . . . iii

Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Speciﬁcations . . . . . . . . . . . . . . . . . . . . . . . . . . vi

1 Getting Started 1 – 1

1.1 Introduction to the Instrument . . . . . . . . . . . . . 1 – 2

1.2 Front-Panel Operation . . . . . . . . . . . . . . . . . . 1 – 3

1.3 Connections . . . . . . . . . . . . . . . . . . . . . . . . 1 – 5

1.4 Power-On . . . . . . . . . . . . . . . . . . . . . . . . . 1 –6

1.5 Restoring the Default Conﬁguration . . . . . . . . . . 1 – 6

1.6 SIM Interface . . . . . . . . . . . . . . . . . . . . . . . . 1 – 7

2 Description of Operation 2 – 1

2.1 Signal Connections and Grounding . . . . . . . . . . . 2 – 2

2.2 Autocalibration . . . . . . . . . . . . . . . . . . . . . . 2– 2

2.3 AC Characteristics . . . . . . . . . . . . . . . . . . . . 2 – 3

2.4 Clock Stopping . . . . . . . . . . . . . . . . . . . . . . 2 – 4

3 Remote Operation 3 – 1

3.1 Index of Common Commands . . . . . . . . . . . . . . 3 – 2

3.2 Alphabetic List of Commands . . . . . . . . . . . . . . 3– 4

3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3– 6

3.4 Commands . . . . . . . . . . . . . . . . . . . . . . . . . 3 – 7

3.5 Status Model . . . . . . . . . . . . . . . . . . . . . . . . 3 – 19

4 Performance Veriﬁcation 4 – 1

4.1 Verifying the DC Accuracy . . . . . . . . . . . . . . . . 4 – 2

4.2 Verifying AC Performance . . . . . . . . . . . . . . . . 4– 4

4.3 Noise Characteristics . . . . . . . . . . . . . . . . . . . 4 – 6

4.4 Performance Test Record . . . . . . . . . . . . . . . . . 4 – 8

5 Circuit Description 5 – 1

5.1 Circuit Discussion . . . . . . . . . . . . . . . . . . . . . 5 – 2

5.2 Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . 5– 6

5.3 Schematic Diagrams . . . . . . . . . . . . . . . . . . . 5 – 10

ii Contents

A Index A – 1

SIM983 Scaling Ampliﬁer

General Information

The SIM983 Scaling Ampliﬁer, part of Stanford Research Systems’ Small Instrumentation Modules family, performs the function

= G × (Vin+ V

out

ofs

)

where Vinand V output of the instrument, respectively, G is a user-speciﬁed gain, and V within its resolution.

Safety and Preparation for Use

The front-panel input, front-panel output, and the rear-panel output coaxial (BNC) connectors in the SIM983 are referenced to the Earth, and their outer casings are grounded. No dangerous voltages are generated by the module.

CAUTION

Do not exceed ±15 volts to the Earth at the center terminal of each BNC connector. Do not install substitute parts or perform unauthorized

modiﬁcations to this instrument.

The SIM983 is a single-wide module designed to be used inside the SIM900 Mainframe. Do not turn on the power to the mainframe or apply voltage input to the module until the module is completely inserted into the mainframe and locked in place.

are voltages (up to ±10 V) at the input and the

out

is a user-speciﬁed oﬀset voltage. The instrument is accurate

ofs

iii

iv General Information

Symbol Description

Alternating current

Caution - risk of electric shock

Frame or chassis terminal

Caution - refer to accompanying documents

Earth (ground) terminal

Battery

Fuse

On (supply)

Off (supply)

Symbols you may Find on SRS Products

SIM983 Scaling Ampliﬁer

General Information v

Notation

The following notation will be used throughout this manual:

WARNING

CAUTION

A warning means that injury or death is possible if the instructions are not obeyed.

A caution means that damage to the instrument or other equipment is possible.

Typesetting conventions used in this manual are:

• Front-panel buttons are set as [gain ]; [gain ] is shorthand for “[gain ] & [gain ]”.

• Front-panel indicators are set as OVLD.

• Signal names are set as ¬STATUS.

• Signal levels are set as HIGH.

• Remote command names are set as *IDN?.

• Literal text other than command names is set as OFF.

• Special ASCII characters are set as hCRi.

Remote command examples will all be set in monospaced font. In these examples, data sent by the host computer to the SIM983 are set as straight teletype font, while responses received by the host computer from the SIM983 are set as slanted teletype font.

SIM983 Scaling Ampliﬁer

vi General Information

Speciﬁcations

Performance characteristics

Min Typ Max Units

Input Voltage [1] −10.0 +10.0 V

Coupling DC

Resistance 0.99 1.00 1.01 MΩ

Capacitance 26 pF

Bias current [2] 40 pA

Voltage noise [3, 4], 1 kHz 43 nV/√Hz

10 kHz 38 nV/√Hz

Current noise, 10 kHz 3 fA/√Hz

Terminals Grounded BNC [5]

Gain Absolute value 0.01 19.99

Polarity Inverting, non-inverting

Resolution 0.01

Accuracy [2] ±0.01

Stability ±10 ppm/◦C

Oﬀset [3] Voltage

Resolution, |V

| ≤ 1.999 V 1 mV

ofs

| ≥ 2.00 V 10 mV

ofs

−10.00 +10.00 V

Accuracy [2, 4, 6] ±1 ± 200 mV + ppm

Stability [4] ±20 ± 20 (µV + ppm)/◦C

Settling time [7] 2 s

AC −3dB bandwidth, |G| ≤ 1.00 2.0 MHz

performance Gain-bandwidth product, |G| ≥ 1.00 3.0 MHz

[8] |G| ≥ 2.40 5.0 MHz

|G| ≥ 4.20 10.0 MHz |G| ≥ 9.60 17.0 MHz

Slew rate 70 V/µs

THD, 1 kHz −90 dB

Output Voltage [1] −10.0 +10.0 V

Maximum current ±100 mA

Short circuit duration Indeﬁnite

Resistance 50 Ω

Terminals Grounded BNC, front [5] and rear [9]

Operating Temperature [10] 0 40

◦

Power +5, ±15 V DC

Supply current, +5 V 100 mA

±15 V 300 mA

SIM983 Scaling Ampliﬁer

General Information vii

Conditions:

[1] An overload will be detected and the instrument is not guaranteed to

perform properly if these limits are exceeded, or if |Vin+ V the limits. Continuous application of an input voltage Vinin excess of ±15 V will damage the instrument.

[2] At 23◦C. [3] Referred to input. [4] For |G| ≥ 1. For |G| < 1, the speciﬁcation applies to the output-referred

noise and oﬀset.

[5] Amphenol 31–10–4052 or similar. [6] Following an autocalibration at (23±5)◦C within 24 hours; following

a 2-hour warmup.

[7] To within 0.1% of the ﬁnal value. [8] The gain-bandwidth product (GBP) determines the −3 dB bandwidth:

For gain G, the bandwidth is GBP/|G|.

[9] Tyco 227169–4 or similar.

[10] Non-condensing.

|exceeds

ofs

General characteristics

Interface Serial (RS–232) through SIM interface

Connectors BNC (2 front [5], 1 rear [9]); DB–15 (male) SIM interface

Weight 1.5 lbs

Dimensions 1.500W × 3.600H × 7.000D

SIM983 Scaling Ampliﬁer

viii General Information

SIM983 Scaling Ampliﬁer

1 Getting Started

In This Chapter

This chapter gives you the necessary information to get started quickly with your SIM983 Scaling Ampliﬁer.

1.1 Introduction to the Instrument . . . . . . . . . . . . 1 – 2

1.1.1 Front and rear panels . . . . . . . . . . . . . . 1 – 3

1.2 Front-Panel Operation . . . . . . . . . . . . . . . . . 1 – 3

1.2.1 Polarity . . . . . . . . . . . . . . . . . . . . . 1 – 3

1.2.2 Gain . . . . . . . . . . . . . . . . . . . . . . . 1 – 3

1.2.3 Oﬀset . . . . . . . . . . . . . . . . . . . . . . . 1 – 4

1.2.4 Overload . . . . . . . . . . . . . . . . . . . . . 1 – 4

1.3 Connections . . . . . . . . . . . . . . . . . . . . . . . 1 – 5

1.4 Power-On . . . . . . . . . . . . . . . . . . . . . . . . 1 – 6

1.5 Restoring the Default Conﬁguration . . . . . . . . 1 – 6

1.6 SIM Interface . . . . . . . . . . . . . . . . . . . . . . 1 – 7

1.6.1 SIM interface connector . . . . . . . . . . . . 1 – 7

1.6.2 Direct interfacing . . . . . . . . . . . . . . . . 1 – 7

1 – 1

1 – 2 Getting Started

Input BNC

1 kΩ input protection

1.00 MΩ

High-impedance buffer

Programmable offset

Invert

noninverting polarity

inverting polarity

frequency compensation

Programmable gain (inverting)

37 Ω

13 Ω

Output BNC, rear

Output BNC, front

1.1 Introduction to the Instrument

The SIM983 Scaling Ampliﬁer provides ﬁne adjustable gain and oﬀset control of an analog signal. The gain (0.01 ≤ |G| ≤ 19.99), its polarity (inverting or non-inverting), and the oﬀset voltage (−10.00 V ≤ V or remotely. A remote computer can access the module through theremote interface SIM900 Mainframe, using RS–232 or GPIB.

The digital control circuitry in the SIM983 is designed with a special clock-stopping architecture. The microcontroller is turned on only when the polarity, gain, or oﬀset are being changed, during remote communications, or when an overload condition occurs. This guarantees that no digital noise contaminates low-level analog signals. A user-commanded autocalibration procedure allows one to controlDC accuracy the input-referred oﬀset to within ±1 mV of the desired value.

The ampliﬁer’s high slew rate allows it to output a ±10 V peak-peak sine wave at a frequency of 1 MHz. The gain stage of the ampliﬁerAC performance is compensated in a ﬂexible fashion to provide a sensible pulse response, so the bandwidth of the instrument is adjusted according to its gain.1The ample output current in the SIM983 permits one to drive a 50 Ω load.

≤ +10.00 V) can be set from either the front panel

ofs

If the maximum input voltage is exceeded, or the gain or oﬀset cause the output voltage to exceed its maximum, the appropriate overload LED turns on. If armed, the module also generates a status signal to alert the user of the overload condition. The SIM983 can be operated outside the SIM900 Mainframe by powering it with its required DC voltages.

A block diagram of the ampliﬁer is shown below in Figure 1.1.

Figure 1.1: The SIM983 block diagram.

The gain-bandwidth product changes with the gain.

SIM983 Scaling Ampliﬁer

1.2 Front-Panel Operation 1 – 3

1.1.1 Front and rear panels

1.2 Front-Panel Operation

1.2.1 Polarity

The polarity is the sign of the gain. It is indicated on the upper display of the front panel. To change the polarity, press the [polarity] button once. Holding this button has no eﬀect.

Pressing [polarity] has no eﬀect on the input-referred oﬀset. However, a simultaneous press of [polarity] and one of [gain ] has a special meaning. This press initiates autocalibration (Section 2.2).

1.2.2 Gain

The gain G can be set to an absolute value between 0.01 and 19.99. To raise or lower the absolute value of the gain, press the button [gain ] or the button [gain ]. The decimal point position of the gain displayed on the front panel is ﬁxed, so the resolution of the gain is 0.01. If [gain ] is pressed when the gain G = ±19.99, the press has no eﬀect. If [gain ] is pressed when G = ±0.01, the press has no eﬀect. Pressing either [gain ] does not change the polarity.

Figure 1.2: The SIM983 front and rear panels.

SIM983 Scaling Ampliﬁer

1 – 4 Getting Started

If one of [gain ] is pressed and held, the gain is continuously adjusted. The rate of the adjustment increases as the button is held. If the absolute value of the gain is being lowered, the rate of the adjustment changes as |G| crosses 1.00, and possibly again as |G|crosses 0.10.

If both [gain ] and [gain ] buttons are pressed at the same time, theresetting gain absolute value of the gain is reset to 1.00. This action does not change the polarity.

Pressing one of [gain ] and [polarity] at the same time has a special meaning. This press initiates autocalibration (Section 2.2).

1.2.3 Offset

The input-referred voltage oﬀset V

can be set to a value

ofs

between −10.00 V and +10.00V. Its value, in volts, is shown on the second line of displays on the front panel of the ampliﬁer.

To increase or decrease the oﬀset, press the button [oﬀset ] or the button [oﬀset ]. Unlike the gain, the “up” and “down” buttons adjust the oﬀset, not its absolute value. Thus, for example, pressing [oﬀset ] when V

= −5.48 V. If [oﬀset ] is pressed when V

ofs

press has no eﬀect. If [oﬀset ] is pressed when V

= −5.49 V makes

ofs

= +10.00 V, the

ofs

= −10.00 V, the

ofs

press has no eﬀect.

Between the values −2.00 V < V

< +2.00 V, the oﬀset is selected

ofs

with 0.001 V resolution; the position of the decimal point on the frontpanel displays is shifted to the left. Although the resolution is 0.01 V for |V Thus, for example, setting V

| ≥ 2.00 V, the accuracy of the oﬀset is still ±1 mV ± 0.02%.

ofs

= −5.48 V produces V

ofs

= (−5.480

ofs

± 0.001 ± 0.001) = (−5.480 ± 0.002) V.

If one of [oﬀset ] is pressed and held, the oﬀset is continuously adjusted. The rate of the adjustment increases as the button is held. If the value crosses the threshold V

= ±2.00 V, the rate changes

ofs

appropriately.

1.2.4 Overload

If both [oﬀset ] and [oﬀset ] buttons are pressed at the same time, theresetting oﬀset oﬀset is reset to 0.000 V.

There are two overload indicators, one OVLD LED in the INPUT block and one OVLD LED in the OUTPUT block of the front panel. The overload signal can also be asserted on the ¬STATUS pin. See Section 3.5.

SIM983 Scaling Ampliﬁer

1.3 Connections 1 – 5

1.2.4.1 Input overload

An overload condition is recognized and the input OVLD LED is activated if the absolute value of the voltage applied to the input exceeds certain limits. These limits are typically ±10.0 V, and areoverload limits between

1.2.4.2 Output overload

1.3 Connections

−10.4 V ≤ V

≤ −9.9 V, 9.9 V ≤ V

min

max

≤ 10.4 V.

The overloaded state is also recognized, and the input overload LED activated, if the sum of the input voltage and the commanded oﬀset,

|Vin+V

|, exceeds these limits. To distinguish between the two input

ofs

overload possibilities, use the command OVLD?. The overload LED

stays on for a minimum of 50 ms; after this time it turns oﬀ if the overload condition has ceased.

An overload condition is recognized and the output OVLD LED is activated if the absolute value |G × (Vin+ V

)| exceeds the limits in

ofs

Section 1.2.4.1. The overload LED stays on for a minimum of 50 ms; after this time it turns oﬀ if the overload condition has ceased.

For a discussion of the front and rear BNC connections, see Section 2.1. The SIM interface connector is discussed in Section 1.6.1.

SIM983 Scaling Ampliﬁer

1 – 6 Getting Started

1.4 Power-On

The instrument retains the values of the gain and the oﬀset in nonvolatile memory. Upon power-on, those settings are restored to their values before the power was turned oﬀ.

The power-on conﬁguration of the remote interface is detailed in Section 3.3.1.

1.5 Restoring the Default Conﬁguration

The default conﬁguration of the SIM983 is G = +1.00, V

= 0.000 V,

ofs

and bandwidth 0 (see Section 2.3.1). This conﬁguration is reached

from the remote interface by issuing the *RST command. To reset

only the gain or the oﬀset to their default values, use button combinations described in Sections 1.2.2 or 1.2.3.

SIM983 Scaling Ampliﬁer

1.6 SIM Interface 1 – 7

1.6 SIM Interface

The primary connection to the SIM983 Scaling Ampliﬁer is the rearpanel DB–15 SIM interface connector. Typically, the SIM983 is mated to a SIM900 Mainframe via this connection, either through one of the internal mainframe slots or the remote cable interface.

It is also possible to operate the SIM983 directly, without using the SIM900 Mainframe. This section provides details on the interface.

1.6.1 SIM interface connector

The DB–15 SIM interface connector carries all the power and communication lines to the instrument. The connector signals are speciﬁed in Table 1.1.

Direction

Pin Signal Src ⇒ Dest Description

1 SIGNAL GND MF ⇒ SIM Ground Reference 1 2 ¬STATUS SIM ⇒ MF Status/service request (GND = asserted, +5 V= idle) 3 RTS MF ⇒ SIM HW handshake (unused in SIM983) 4 CTS SIM ⇒ MF HW handshake (unused in SIM983) 5 ¬REF 10MHZ MF ⇒ SIM 10MHz reference (no connection in SIM983) 6 −5V MF ⇒ SIM Power supply (no connection in SIM983) 7 −15V MF ⇒ SIM Power supply 8 PS RTN MF ⇒ SIM Ground Reference 2

9 CHASSIS GND Chassis ground 10 TXD MF ⇒ SIM Async data (start bit = “0”= +5 V; “1” = GND) 11 RXD SIM ⇒ MF Async data (start bit = “0”= +5 V; “1” = GND) 12 +REF 10MHZ MF ⇒ SIM 10MHz reference (no connection in SIM983) 13 +5V MF ⇒ SIM Power supply 14 +15V MF ⇒ SIM Power supply 15 +24V MF ⇒ SIM Power supply (no connection in SIM983)

1.6.2 Direct interfacing

SIM983 Scaling Ampliﬁer

Table 1.1: SIM interface connector pin assignments, DB–15.

The SIM983 is intended for operation in the SIM900 Mainframe, but users may wish to directly interface the module to their own systems without the use of additional hardware.

The mating connector needed is a standard DB–15 receptacle, such as Tyco part number 747909–2 (or equivalent). Clean, well-regulated supply voltages of ±15.0 V DC, +5.0 V DC must be provided, following the pinout speciﬁed in Table 1.1 and the minimum currents in the table on Page vi. Ground must be provided on Pins 1 and 8, with chassis ground on Pin 9. The ¬STATUS signal may be monitored

1 – 8 Getting Started

on Pin 2 for a low-going TTL-compatible output indicating a status message. See Section 3.5 for the description of status messages.

CAUTION

The SIM983 has no internal protection against reverse polarity, missing supply, or overvoltage on the +5 V and the ±15 V power-supply pins. Supply voltages above 5.5 V on Pin 13, above +16 V on Pin 14, or below −16 V on Pin 7 are likely to damage the instrument. SRS recommends using the SIM983 together with the SIM900 Mainframe for most applications.

1.6.2.1 Direct interface cabling

If the user intends to directly wire the SIM983 independent of the SIM900 Mainframe, communication is usually possible by directly connecting the appropriate interface lines from the SIM983 DB–15 plug to the RS–232 serial port of a personal computer.2Connect RXD from the SIM983 directly to RD on the PC, TXD directly to TD, and similarly RTS→RTS and CTS→CTS. In other words, a null-modemstyle cable is not needed.

To interface directly to the DB–9 male (DTE) RS–232 port typically found on contemporary personal computers, a cable must be made with a female DB–15 socket to mate with the SIM983, and a female DB–9 socket to mate with the PC’s serial port. Separate leads from the DB–15 need to go to the power supply, making what is sometimes know as a “hydra” cable. The pin connections are given in Table 1.2.

DB–15/F to SIM983 Name

DB–9/F

10 ←→3 TxD 11 ←→2 RxD

5 Computer Ground

to Power Supply

7 ←→ −15 V DC 13 ←→ +5 V DC 14 ←→ +15 V DC

1 ←→ Ground 1 (separate wire to Ground)

8 ←→ Ground 2 (separate wire to Ground)

9 ←→ Chassis Ground (separate wire to Ground)

Table 1.2: SIM983 direct interface cable pin assignments.

The distinct Ground References 1 and 2, and the chassis ground, arenote about grounds not directly connected within the SIM983. Ground 1 carries the return

Although the serial interface lines on the DB–15 do not satisfy the minimum voltage levels of the RS–232 standard, these lines are typically compatible with desktop personal computers.

SIM983 Scaling Ampliﬁer

1.6 SIM Interface 1 – 9

currents of digital control signals and the power supplies, whereas the input voltage and the output voltage reference to Ground 2 (Section 2.1.2). When operating in the SIM900, the three grounds are tied together in the SIM900 Mainframe. Grounds 1 and 2 are connected through back-to-back Schottky diodes, so they cannot be more than ∼ ±0.35 V apart. The three ground lines should be separately wired to a single, low-impedance ground source at the power supply.

1.6.2.2 Serial settings

The initial serial port settings at power-on are: baud rate 9600, 8 bits, no parity, 1 stop bit, and no ﬂow control. The baud rate of the SIM983 cannot be changed. Flow control is not implemented in the SIM983.

The parity may be changed with the PARI command.

SIM983 Scaling Ampliﬁer

1 – 10 Getting Started

SIM983 Scaling Ampliﬁer

2 Description of Operation

This chapter provides a number of additional details of the operation of the SIM983.

In This Chapter

2.1 Signal Connections and Grounding . . . . . . . . . 2 – 2

2.2 Autocalibration . . . . . . . . . . . . . . . . . . . . . 2 – 2

2.3 AC Characteristics . . . . . . . . . . . . . . . . . . . 2 – 3

2.4 Clock Stopping . . . . . . . . . . . . . . . . . . . . . 2 – 4

2.1.1 Output drive . . . . . . . . . . . . . . . . . . 2 – 2

2.1.2 Grounds . . . . . . . . . . . . . . . . . . . . . 2 – 2

2.3.1 Bandwidth . . . . . . . . . . . . . . . . . . . . 2 – 3

2.3.2 Slew rate . . . . . . . . . . . . . . . . . . . . . 2 – 3

2 – 1

2 – 2 Description of Operation

2.1 Signal Connections and Grounding

2.1.1 Output drive

The output impedance of the SIM983 Scaling Ampliﬁer is 50 Ω. The ampliﬁer can drive load impedances from ∞ to 50 Ω for the full ±10 V range of output voltage. When driving a 50 Ω load, the gain will be half of that displayed on the front panel.

The rear-panel output connector is wired in parallel with the frontpanel output, and shares some of the output impedance (Figure 1.1). The output stage is not designed to drive two 50 Ω loads simultaneously.

2.1.2 Grounds

Both the input and the output of the SIM983 are referenced to ground. To maintain the DC accuracy of the instrument, there are two separate ground references. Ground 1 (Pin 1 of the SIM interface connector) provides a return path for digital control signals and the power supply currents, while Ground 2 (Pin 8 of the interface connector) serves as the reference point for analog voltages. The outer casings of the input and the output front-panel BNC connectors are tied to Ground 2. The output current of the ampliﬁer returns to the power supply through Ground 2.

2.2 Autocalibration

The outer casing of the rear-panel output BNC is connected to chassis ground, Pin 9 of the DB–15 SIM interface connector. The separate power, analog, and chassis grounds are not directly connected within the ampliﬁer. When operating in the SIM900 Mainframe, the three grounds are tied together inside the mainframe, and through the mainframe to the Earth. Grounds 1 and 2 are connected inside the SIM983 through back-to-back Schottky diodes, so they cannot be more than ∼ ±0.35 V apart.

To ensure DC oﬀset accuracy, the ampliﬁer must be self-calibrated within the 24 hours preceding a measurement. A valid autocalibration must take place at (23 ± 5)◦C with the module warmed up for at least 2 hours at (23 ± 5)◦C. If the module is being used inside the SIM900 Mainframe, the autocalibration must also be inside the mainframe. Otherwise, perform the autocalibration with the same connection to an independent supply as you use for the operation. The autocalibration is only accurate if the output has stabilized within ±15 mV of zero for at least 2 minutes immediately preceding the calibration. However, the gain and the oﬀset need not be at

SIM983 Scaling Ampliﬁer

2.3 AC Characteristics 2 – 3

their default values; after the calibration completes, these values are restored.

Disconnect all inputs and outputs to the SIM983 while performing the au-

tocalibration. To calibrate, issue the command ACAL, or press the but-

ton [polarity] and one of [gain ] at the same time. The calibration completes and the instrument is ready for operation within 2 seconds. If autocalibration is unsuccessful, for example because an external voltage (which cannot be nulled) is applied to the input, the calibration parameters revert to their original values and the com-

mand LDDE? will return Code 1.

Autocalibration does not aﬀect gain accuracy.

2.3 AC Characteristics

2.3.1 Bandwidth

The gain-bandwidth product (GBP) of the SIM983 is a measure of its small-signal behavior, and depends on |G|. Four gain ranges correspond to four values of gain-bandwidth product, as speciﬁed in the table on Page vi. For |G| ≥ 1, the −3 dB small-signal bandwidth of the ampliﬁer is f

−3 dB

(G) & f

(G = 1.00).

−3 dB

= GBP/|G|. For |G| < 1,

−3 dB

2.3.2 Slew rate

The gain-bandwidth product is determined by a compensation capacitor in the feedback path of the gain-stage ampliﬁer. It is possible to override the value of this capacitor, giving the instrument more

bandwidth. To do this, use the command BWTH. If the bandwidth

is altered in this way, the next front-panel button press will return the bandwidth to the value appropriate for the current gain. Cycling the power or performing an autocalibration will also return the bandwidth to its default value for the gain.

If the bandwidth is set to a value other than its default, the ampliﬁer may exhibit slow settling, excessive ringing, or oscillations.

The small-signal settling time of the ampliﬁer is a complex function of its gain and its bandwidth.

The slew rate of an ampliﬁer is a measure of its large-signal behavior. It is the maximum rate of change of the output voltage, measured in V/s. The slew rate (SR) determines the maximum undistorted AC signal that can be output; for a sine-wave output at a frequency f , the maximum peak-peak voltage is |V

max−Vmin

| = SR/(π f ).

The SIM983 is designed to be able to output a full-range sine wave at 1 MHz.

SIM983 Scaling Ampliﬁer

2 – 4 Description of Operation

If the output or an intermediate stage of the ampliﬁer is driven beyond the limits in the table on Page vi, large-signal behavior is not guaranteed.

2.4 Clock Stopping

The microprocessor clock of the SIM983 stops if the module is idle, “freezing” the digital circuitry. The following actions “wake up” the clock:

1. A power-on.

2. A press of a front-panel button.

3. Activity (send or receive) at the remote interface.

4. An overload.

The clock runs for as long as is necessary to complete a gain or oﬀset adjustment, or to communicate the output of a query through the remote interface. However, the clock will remain active for as long as the overload condition exists.

This default behavior can be modiﬁed with the remote com-

mand AWAK. Setting AWAKON will prevent the clock from stopping. The module returns to AWAKOFF upon power-on.

SIM983 Scaling Ampliﬁer

3 Remote Operation

In This Chapter

This chapter describes operating the SIM983 over the serial interface.

3.1 Index of Common Commands . . . . . . . . . . . . 3 – 2

3.2 Alphabetic List of Commands . . . . . . . . . . . . 3 – 4

3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . 3 – 6

3.3.1 Power-on conﬁguration . . . . . . . . . . . . 3 – 6

3.3.2 Buﬀers . . . . . . . . . . . . . . . . . . . . . . 3 – 6

3.3.3 Device Clear . . . . . . . . . . . . . . . . . . . 3 – 6

3.4 Commands . . . . . . . . . . . . . . . . . . . . . . . 3 – 7

3.4.1 Command syntax . . . . . . . . . . . . . . . . 3 – 7

3.4.2 Notation . . . . . . . . . . . . . . . . . . . . . 3 – 8

3.4.3 Examples . . . . . . . . . . . . . . . . . . . . 3 – 8

3.4.4 General commands . . . . . . . . . . . . . . . 3 – 9

3.4.5 Conﬁguration commands . . . . . . . . . . . 3 – 10

3.4.6 Calibration commands . . . . . . . . . . . . . 3 – 11

3.4.7 Status commands . . . . . . . . . . . . . . . . 3 – 11

3.4.8 Interface commands . . . . . . . . . . . . . . 3 – 14

3.4.9 Serial communication commands . . . . . . 3 – 17

3.5 Status Model . . . . . . . . . . . . . . . . . . . . . . 3 – 19

3.5.1 Status Byte (SB) . . . . . . . . . . . . . . . . . 3 – 20

3.5.2 Service Request Enable (SRE) . . . . . . . . . 3 – 20

3.5.3 Standard Event Status (ESR) . . . . . . . . . 3 – 20

3.5.4 Standard Event Status Enable (ESE) . . . . . 3 – 21

3.5.5 Communication Error Status (CESR) . . . . . 3 – 21

3.5.6 Communication Error Status Enable (CESE) 3 – 22

3.5.7 Overload Status (OLSR) . . . . . . . . . . . . 3 – 22

3.5.8 Overload Status Enable (OLSE) . . . . . . . . 3 – 23

3 – 1

3 – 2 Remote Operation

3.1 Index of Common Commands

Symbol Deﬁnition

f Floating-point value i Bit number (0–7) j Unsigned integer (0–255) m Unsigned integer (0–3) z Literal token

(?) Required for queries; illegal for set commands

var Parameter always required

{var} Required parameter for set commands; illegal for queries [var] Optional parameter for both set and query forms

General

HELP(?) 3 – 9 Instrument Help AWAK(?) {z} 3 – 10 Keep Clock Awake

Conﬁguration

GAIN(?) {f } 3 – 10 Gain OFST(?) {f } 3 – 10 Oﬀset BWTH(?) [m] 3 – 11 Bandwidth

Calibration

ACAL 3 – 11 Autocalibration

Status

*CLS 3 – 11 Clear Status *STB? [i] 3 – 12 Status Byte *SRE(?) [i,] {j} 3 – 12 Service Request Enable *ESR? [i] 3 – 12 Standard Event Status *ESE(?) [i,] {j} 3 – 12 Standard Event Status Enable CESR? [i] 3 – 12 Communication Error Status CESE(?) [i,] {j} 3 – 13 Communication Error Status Enable OLSR? [i] 3 – 13 Overload Status OLSE(?) [i,] {j} 3 – 13 Overload Status Enable PSTA(?) {z} 3 – 13 Pulse ¬STATUS Mode LBTN? 3 – 13 Last Button OVLD? 3 – 14 Overload

Interface

*RST 3 – 14 Reset *IDN? 3 – 15 Identify *TST? 3 – 15 Self Test

SIM983 Scaling Ampliﬁer

3.1 Index of Common Commands 3 – 3

*OPC(?) 3 – 15 Operation Complete CONS(?) {z} 3 – 15 Console Mode LEXE? 3 – 16 Execution Error LCME? 3 – 16 Command Error LDDE? 3 – 17 Device Error TOKN(?) {z} 3 – 17 Token Mode TERM(?) {z} 3 – 17 Response Termination

Serial Communications

PARI(?) {z} 3 – 18 Parity

SIM983 Scaling Ampliﬁer

3 – 4 Remote Operation

3.2 Alphabetic List of Commands

*CLS 3 – 11 Clear Status *ESE(?) [i,] {j} 3 – 12 Standard Event Status Enable *ESR? [i] 3 – 12 Standard Event Status *IDN? 3 – 15 Identify *OPC(?) 3 – 15 Operation Complete *RST 3 – 14 Reset *SRE(?) [i,] {j} 3 – 12 Service Request Enable *STB? [i] 3 – 12 Status Byte *TST? 3 – 15 Self Test

ACAL 3 – 11 Autocalibration AWAK(?) {z} 3 – 10 Keep Clock Awake

BWTH(?) [m] 3 – 11 Bandwidth

CESE(?) [i,] {j} 3 – 13 Communication Error Status Enable CESR? [i] 3 – 12 Communication Error Status CONS(?) {z} 3 – 15 Console Mode

GAIN(?) {f } 3 – 10 Gain

HELP(?) 3 – 9 Instrument Help

LBTN? 3 – 13 Last Button LCME? 3 – 16 Command Error LDDE? 3 – 17 Device Error LEXE? 3 – 16 Execution Error

OFST(?) {f } 3 – 10 Oﬀset OLSE(?) [i,] {j} 3 – 13 Overload Status Enable OLSR? [i] 3 – 13 Overload Status OVLD? 3 – 14 Overload

SIM983 Scaling Ampliﬁer

3.2 Alphabetic List of Commands 3 – 5

PARI(?) {z} 3 – 18 Parity PSTA(?) {z} 3 – 13 Pulse ¬STATUS Mode

TERM(?) {z} 3 – 17 Response Termination TOKN(?) {z} 3 – 17 Token Mode

SIM983 Scaling Ampliﬁer

3 – 6 Remote Operation

3.3 Introduction

Remote operation of the SIM983 is through a simple command language documented in this chapter. Both set and query forms of most commands are supported, allowing the user complete control of the ampliﬁer from a remote computer, either through the SIM900 Mainframe or directly via RS–232 (see Section 1.6.2.1).

See Table 1.1 for the speciﬁcation of the DB–15 SIM Interface Connector.

3.3.1 Power-on conﬁguration

The initial settings for the remote interface are 9600 baud with no

parity and no ﬂow control, and with local echo disabled (CONS OFF).

The values of the gain and the oﬀset are retained in non-volatile memory. Upon power-on, those settings are restored to their values before the power was turned oﬀ. The bandwidth is set to the value appropriate for the stored gain.

Where appropriate, the default or power-on value for parameters is listed in boldface in the command descriptions.

3.3.2 Buffers

3.3.3 Device Clear

The SIM983 stores incoming bytes from the host interface in a 64byte input buﬀer. Characters accumulate in the input buﬀer until a command terminator (either hCRi or hLFi) is received, at which point the message is parsed and executed. Query responses from the SIM983 are buﬀered in a 64-byte output queue.

If the input buﬀer overﬂows, then all data in both the input buﬀer and the output queue are discarded, and an error is recorded in the CESR and ESR status registers.

The SIM983 host interface can be asynchronously reset to its poweron conﬁguration by sending an RS–232-style hbreakisignal. From the

SIM900 Mainframe, this is accomplished with the SRST command;

if directly interfacing via RS–232, then use a serial break signal. After

receiving the Device Clear, the CONS mode is turned OFF. Note that

this only resets the communication interface; the basic function of

the SIM983 is left unchanged; to reset the ampliﬁer, use *RST. The Device Clear signal will also terminate the output of the HELP?

command from the SIM983.

SIM983 Scaling Ampliﬁer

3.4 Commands 3 – 7

3.4 Commands

This section provides syntax and operational descriptions for remote commands.

3.4.1 Command syntax

The four letter mnemonic (shown in CAPS) in each command se-

quence speciﬁes the command. The rest of the sequence consists of parameters.

Commands may take either set or query form, depending on whether

the “?” character follows the mnemonic. Set only commands are listed without the “?”, query only commands show the “?” after the mnemonic, and optionally query commands are marked with a “(?)”.

Parameters shown in { } and [ ] are not always required. Parameters in { } are required to set a value, and should be omitted for queries. Parameters in [ ] are optional in both set and query commands. Parameters listed without surrounding characters are always required.

Do not send ( ) or { } or [ ] as part of the command.

Multiple parameters are separated by commas. Multiple commands may be sent on one command line by separating them with semicolons (;) so long as the input buﬀer does not overﬂow. Commands are terminated by either hCRi or hLFi characters. Null commands and whitespaces are ignored. Execution of the command does not begin until the command terminator is received.

Token parameters (generically shown as z in the command descrip-tokens tions) can be speciﬁed either as a keyword or as an integer value. Command descriptions list the valid keyword options, with each keyword followed by its corresponding integer value. For example, to set the response termination sequence to hCRi+hLFi, the following two commands are equivalent:

TERM CRLF —or— TERM 3

For queries that return token values, the return format (keyword or

integer) is speciﬁed with the TOKN command.

SIM983 Scaling Ampliﬁer

3 – 8 Remote Operation

3.4.2 Notation

The following table summarizes the notation used in the command descriptions:

Symbol Deﬁnition

f Floating-point value i Bit number (0–7) j Unsigned integer (0–255) m Unsigned integer (0–3) z Literal token

(?) Required for queries; illegal for set commands

var Parameter always required

{var} Required parameter for set commands; illegal for queries [var] Optional parameter for both set and query forms

3.4.3 Examples

Each command is provided with a simple example illustrating its usage. In these examples, all data sent by the host computer to the SIM983 are set as straight teletype font, while responses received by the host computer from the SIM983 are set as slanted teletype font.

The usage examples vary with respect to set/query, optional parameters, and token formats. These examples are not exhaustive, and are intended to provide a convenient starting point for user programming.

SIM983 Scaling Ampliﬁer

3.4 Commands 3 – 9

3.4.4 General commands

Instrument HelpHELP(?)

Outputs a condensed version of Section 3.4 to the remote interface.

HELP may be used with or without the query sign, with the same

eﬀects.

HELP?Example:

Notation: f is a floating-point number; i is bit number (0..7); j is an 8-bit unsigned integer (0..255); m is a 2-bit unsigned integer (0..3); z is a token (?) question required for queries, illegal for set commands; [] = parameter is optional for both set and query forms; {} = parameter is required to set, illegal for queries; parameter without brackets is always required; the brackets themselves should not be sent.

General commands: HELP? - Send this text. AWAK(?) {z} - Keep the module clock awake.

Configuration commands: GAIN(?) {f} - Set/query gain. OFST(?) {f} - Set/query offset. BWTH(?) [m] - Output bandwidth.

Calibration commands: ACAL - One-time autocalibration.

Status commands: *CLS - Clear Status. *STB? [i] - Query the Status Byte. *SRE(?) [i,] {j} - Service Request Enable. *ESR? [i] - Query Standard Event Status register. *ESE(?) [i,] {j} - Standard Event Status Enable. CESR? [i] - Query the Communications Error Status. CESE(?) [i,] {j} - Communications Error Status Enable. OLSR? [i] - Query Overload Status register. OLSE(?) [i,] {j} - Overload Status Enable. PSTA(?) {z} - Pulse Status or change its level. LBTN? - Which button last pressed? OVLD? - Input or output currently overloaded?

SIM983 Scaling Ampliﬁer

3 – 10 Remote Operation

Interface commands: *RST - Reset to known state. *IDN? - Identify. *TST? - Does nothing. *OPC(?) - Operation complete. CONS(?) {z} - Console OFF/ON. LEXE? - Last Execution Error. LCME? - Last Communications Error. LDDE? - Last Device-Dependent Error. TOKN(?) {z} - Turn token mode OFF/ON. TERM(?) {z} - Cmd line end (NONE, CR, LF, CRLF, LFCR).

Serial interface command (baud rate is always 9600): PARI(?) {z} - Parity (NONE, EVEN, ODD, MARK, SPACE).

Keep Clock AwakeAWAK(?) {z}

Set (query) the SIM983 keep-awake mode {to z = (OFF 0, ON 1)}.

Ordinarily, the clock oscillator for the SIM983 microcontroller is held in a stopped state, and only enabled during processing of events

(Section 2.4). Setting AWAK ON forces the clock to stay running, and

is useful only for diagnostic purposes.

AWAK ONExample:

3.4.5 Conﬁguration commands

GainGAIN(?) {f }

Set (query) the ampliﬁer gain {to f}. The module accepts signed ﬂoating-point values in the ranges −19.99 ≤ f ≤ −0.01, 0.01 ≤ f ≤ 19.99. The reset value is f = +1.00 .

After a GAIN set command, the bandwidth is set to the value appro-

priate for the new gain. Gain queries do not alter the bandwidth.

GAIN 1.4232E1; GAIN?Example:

+14.23

OﬀsetOFST(?) {f }

Set (query) the oﬀset of the ampliﬁer {to f volts}. The module accepts signed ﬂoating-point values in the range −10.000 ≤ f ≤ 10.000. The reset value is f = 0.000 .

Setting or querying the oﬀset does not change the bandwidth.

SIM983 Scaling Ampliﬁer

3.4 Commands 3 – 11

OFST -7.032; OFST?Example:

-07.030

BandwidthBWTH(?) [m]

Set (query) the gain-bandwidth product of the ampliﬁer [to m]. Allowed values of the optional parameter are 0 through 3, with a larger value corresponding to a greater gain-bandwidth. When the gain is set from the front panel or from the remote interface, the bandwidth automatically reverts to the following:

Range Bandwidth m GBP, MHz min

0.01 ≤ |G| ≤ 2.39 0 3.0 (|G| ≥ 1.00)

2.40 ≤ |G| ≤ 4.19 1 5.0

4.20 ≤ |G| ≤ 9.59 2 10.0

9.60 ≤ |G| ≤ 19.99 3 17.0

The bandwidth is also automatically selected from this table if the optional parameter is omitted.

GAIN 17; BWTH 1; BWTH?Example:

GAIN 17; BWTH?

3.4.6 Calibration commands

AutocalibrationACAL

Perform a self-calibration (Section 2.2). Make sure to disconnect all inputs and outputs to the SIM983, and to set the output to zero. Remote

commands are not processed until ACAL is complete.

ACALExample: LDDE?

checks for success of an autocalibration.

3.4.7 Status commands

The Status commands query and conﬁgure registers associated with status reporting of the SIM983. See Section 3.5 for the status model.

Clear Status*CLS *CLS immediately clears the ESR, CESR, and OLSR status registers.

*CLSExample:

SIM983 Scaling Ampliﬁer

3 – 12 Remote Operation

Status Byte*STB? [i]

Query the Status Byte register [Bit i].

Execution of the *STB? query (without the optional Bit i) always causes the ¬STATUS signal to be deasserted. Note that *STB? i will

not clear ¬STATUS, even if Bit i is the only bit presently causing the ¬STATUS signal.

*STB?Example:

Service Request Enable*SRE(?) [i,] {j}

Set (query) the Service Request Enable register [Bit i] {to j}.

*SRE 0,1Example:

Standard Event Status*ESR? [i]

Query the Standard Event Status Register [Bit i].

Upon execution of *ESR?, the returned bit(s) of the ESR register are

cleared.

*ESR?Example:

Standard Event Status Enable*ESE(?) [i,] {j}

Set (query) the Standard Event Status Enable register [Bit i] {to j}.

*ESE 6,1Example: ESE?

Communication Error StatusCESR? [i]

Query the Communication Error Status Register [Bit i].

Upon executing a CESR? query, the returned bit(s) of the CESR reg-

ister are cleared.

CESR?Example:

SIM983 Scaling Ampliﬁer

3.4 Commands 3 – 13

Communication Error Status EnableCESE(?) [i,] {j}

Set (query) the Communication Error Status Enable register [Bit i] {to j}.

CESE?Example:

Overload StatusOLSR? [i]

Query the Overload Status Register [Bit i].

Upon executing an OLSR? query, the returned bit(s) of the OLSR reg-

ister are cleared.

OLSR?Example:

Overload Status EnableOLSE(?) [i,] {j}

Set (query) the Overload Status Enable register [Bit i] {to j}.

OLSE 4Example:

Pulse ¬STATUS ModePSTA(?) {z}

Set (query) the Pulse ¬STATUS mode {to z = (OFF 0, ON 1)}.

When PSTA ON is set, all new service requests will only pulse the

¬STATUS signal LOW (for a minimum of 1 µs). The default behavior

is to latch ¬STATUS LOW until a *STB? query is received. A reset does not alter PSTA. The value in boldface above is the

power-on value.

PSTA?Example:

OFF

Last ButtonLBTN?

Query the number of the last button pressed. The response is

LBTN? Last button

1 [polarity] 2 [gain ] 3 [gain ] 4 [oﬀset ] 5 [oﬀset ] 6 Both [gain ] and [gain ] (reset gain) 7 Both [oﬀset ] and [oﬀset ] (reset oﬀset) 8 One of [gain ] and [polarity] (autocalibrate)

SIM983 Scaling Ampliﬁer

3 – 14 Remote Operation

The value 0 is returned if no button was pressed since the last LBTN?. A query of LBTN? always clears the button code, so a subse-

quent LBTN? will return 0.

LBTN?Example:

OverloadOVLD?

Query the current overload condition. The response is

OVLD? Overloaded

1 Input 2 Input + oﬀset 4 Output

Combination overloads are reported by summing the values of the individual overload ﬂags. This command complements the OLSR status register described in Section 3.5.7, and the three overload ﬂags correspond one-to-one with bits in OLSR. However, once cleared

by OLSR? or *CLS, the overload status bits will stay cleared even

though the overload condition may persist and remain reported

by OVLD?.

3.4.8 Interface commands

OVLD?Example:

implies that the input is not overloaded; the intermediate stage (Vin+ V

) is overloaded; and the output is overloaded.

ofs

The Interface commands provide control over the interface between the SIM983 and the host computer.

Reset*RST

Reset the SIM983 to its default conﬁguration.

*RST sets the following:

• Clock oscillator to stop during idle time (AWAKOFF).

• Gain to +1.00.

• Oﬀset to 0.000 V.

• Bandwidth to 0.

• The token mode to OFF.

*RST does not aﬀect PSTA, CONS, TERM, and all service-enable registers (*SRE, *ESE, CESE, or OLSE).

SIM983 Scaling Ampliﬁer

3.4 Commands 3 – 15

*RSTExample: CONS?

Identify*IDN?

Query the device identiﬁcation string.

The identiﬁcation string is formatted as:

Stanford Research Systems,SIM983,s/n******,ver#.###

where SIM983 is the model number, ****** is a 6-digit serial number, and #.### is the ﬁrmware revision level.

*IDN?Example:

Stanford Research Systems,SIM983,s/n004900,ver2.0

Self Test*TST?

There is no internal self-test in the SIM983 after the power-on, so this query always returns 0.

*TST?Example:

Operation Complete*OPC(?)

Sets the OPC ﬂag in the ESR register.

The query form *OPC? writes a 1 into the output queue when com-

plete, but does not aﬀect the ESR register.

*OPC?Example:

Console ModeCONS(?) {z}

Set (query) the console mode {to z = (OFF 0, ON 1)}.

CONScauses each character received at the input buﬀer to be copied

to the output queue.

A reset does not alter CONS. The value in boldface above is the power-on value. CONSis set to OFF upon Device Clear.

CONS ONExample:

SIM983 Scaling Ampliﬁer

3 – 16 Remote Operation

Execution ErrorLEXE? Query the Last Execution Error code. A query of LEXE? always

clears the error code, so a subsequent LEXE? will return 0. Valid

codes are:

Value Deﬁnition

0 No execution error since last LEXE?

1 Illegal value 2 Wrong token 3 Invalid bit

*STB? 12; LEXE?; LEXE?Example:

3 0

The error (3, ”Invalid bit”) is because *STB? only allows bit-speciﬁc queries of 0–7. The second read of LEXE? returns 0.

Command ErrorLCME? Query the Last Command Error code. A query of LCME? always

clears the error code, so a subsequent LCME? will return 0. Valid

codes are:

Value

Deﬁnition

0 No command error since last LCME?

1 Illegal command 2 Undeﬁned command 3 Illegal query 4 Illegal set 5 Missing parameter(s) 6 Extra parameter(s) 7 Null parameter(s) 8 Parameter buﬀer overﬂow

9 Bad ﬂoating point 10 Bad integer 11 Bad integer token 12 Bad token value 14 Unknown token

*IDNExample: LCME?

The error (4, ”Illegal set”) is due to the missing “?”.

SIM983 Scaling Ampliﬁer

3.4 Commands 3 – 17

Device ErrorLDDE? Query the Last Device-Dependent Error code. A query of LDDE?

always clears the error code, so a subsequent LDDE? will return 0.

Valid codes are:

Value Deﬁnition

0 No execution error since last LEXE?

1 Unable to autocalibrate

ACALExample: LDDE?

indicates a successful autocalibration.

Token ModeTOKN(?) {z}

Set (query) the token query mode {to z = (OFF 0, ON 1)}.

If TOKN ON is set, then queries to the SIM983 that return tokens will

return a text keyword; otherwise they return a decimal integer value.

Thus, the only possible responses to the TOKN?query are ON and 0.

TOKN OFFExample:

Response TerminationTERM(?) {z}

Set (query) the htermi sequence {to z = (NONE 0, CR 1, LF 2, CRLF 3, or LFCR 4)}.

The htermi sequence is appended to all query responses sent by the module, and is constructed of ASCII character(s) 13 (carriage return) and 10 (line feed). The token mnemonic gives the sequence of characters.

A reset does not alter TERM. The value in boldface above is the

power-on value.

TOKN ON; TERM?Example:

CRLF

3.4.9 Serial communication commands

Note that the SIM983 can only support a single baud rate of 9600, and does not support ﬂow control. A reset does not change the serial interface settings; use Device Clear.

SIM983 Scaling Ampliﬁer

3 – 18 Remote Operation

ParityPARI(?) {z}

Set (query) the parity {to z = (NONE 0, ODD 1, EVEN 2, MARK 3,

SPACE 4)}. The value in boldface is the power-on value.

TOKN ON; PARI?Example:

EVEN

SIM983 Scaling Ampliﬁer

3.5 Status Model 3 – 19

CESB

MSS

ESB

IDLE

undef

OLSB

Status Byte

SB SRE

OPC: Operation Complete

INP: Input Buffer Error

DDE: Device Error

EXE: Execution Error

CME: Command Error

URQ: User Request

PON: Power On

QYE: Query Error

ESR ESE

Standard Event Status

PARITY: Parity Error

FRAME: Framing Error

HWOVRN: Hardware Input Overrun

OVR: Input Buffer Overrun

RTSH: RTS Halted

CTSH: CTS Halted

DCAS: Device Clear

NOISE: Noise Error

CESR CESE

Communication Error Status

Input

Input + Offset

undef

Output

OLSR OLSE

Overload Status

STATUS

3.5 Status Model

The SIM983 status registers follow the hierarchical IEEE–488.2 for-status registers mat. A block diagram of the status register array is given in Figure 3.1.

Event Registers : These read-only registers record the occurrence of deﬁned

SIM983 Scaling Ampliﬁer

Enable Registers : These read/write registers deﬁne a bitwise mask for their cor-

Figure 3.1: Status register model for the SIM983 Scaling Ampliﬁer.

There are two categories of registers in the SIM983 status model:

events. If the event occurs, the corresponding bit is set to 1. Upon querying an event register, all set bits within it are cleared. These are sometimes known as “sticky bits,” since once set, a bit can only be cleared by reading its value. Event register names end with SR.

responding event register. If a bit position is set in an event register while the same bit position is also set in the enable register, then the corresponding summary bit message is set. Enable register names end with SE.

3 – 20 Remote Operation

At power-on, all status registers are cleared.

3.5.1 Status Byte (SB)

The Status Byte is the top-level summary of the SIM983 status model. When masked by the Service Request Enable register, a bit set in the Status Byte causes the ¬STATUS signal to be asserted on the rearpanel SIM interface connector.

Weight Bit Flag

1 0 OLSB 2 1 undef (0) 4 2 undef (0)

8 3 undef (0) 16 4 IDLE 32 5 ESB 64 6 MSS

128 7 CESB

OLSB : Overload Summary Bit. Indicates whether one or more of the

enabled ﬂags in the Overload Status Register has become true.

IDLE : Indicates that the input buﬀer is empty and the command

parser is idle. Can be used to help synchronize SIM983 query responses.

ESB : Event Status Bit. Indicates whether one or more of the enabled

events in the Standard Event Status Register is true.

MSS : Master Summary Status. Indicates whether one or more of the

enabled status messages in the Status Byte register is true.

CESB : Communication Error Summary Bit. Indicates whether one or

more of the enabled ﬂags in the Communication Error Status Register has become true.

3.5.2 Service Request Enable (SRE)

Each bit in the SRE corresponds one-to-one with a bit in the SB register, and acts as a bitwise AND of the SB ﬂags to generate MSS. Bit 6 of the SRE is undeﬁned—setting it has no eﬀect, and reading it always

returns 0. This register is set and queried with the *SRE(?)command.

At power-on, this register is cleared.

3.5.3 Standard Event Status (ESR)

The Standard Event Status Register consists of 8 event ﬂags. These event ﬂags are all “sticky bits” that are set by the corresponding

events, and cleared only by reading or with the *CLS command. Reading a single bit (with the *ESR? i query) clears only Bit i.

SIM983 Scaling Ampliﬁer

3.5 Status Model 3 – 21

Weight Bit Flag

1 0 OPC

2 1 INP

4 2 QYE

8 3 DDE 16 4 EXE 32 5 CME 64 6 URQ

128 7 PON

OPC : Operation Complete. Set by the *OPC command.

INP : Input buﬀer error. Indicates data has been discarded from the

input buﬀer.

QYE : Query Error. Indicates data in the output queue has been lost.

DDE : Device-Dependent Error. Indicates a failed autocalibration.

EXE : Execution Error. Indicates the error in a command that was

successfully parsed. Out-of-range parameters are an example.

CME : Command Error. Indicates a command parser-detected error.

URQ : User Request. Indicates that a front-panel button was pressed.

PON : Power On. Indicates that an oﬀ-to-on transition has occurred.

3.5.4 Standard Event Status Enable (ESE)

The ESE acts as a bitwise AND with the ESR register to produce the single-bit ESB message in the Status Byte Register (SB). The register

can be set and queried with the *ESE(?) command.

At power-on, this register is cleared.

3.5.5 Communication Error Status (CESR)

The Communication Error Status Register consists of 8 event ﬂags; each of the ﬂags is set by the corresponding event, and cleared only

by reading the register or with the *CLS command. Reading a single bit (with the CESR? i query) clears only Bit i.

Weight Bit Flag

1 0 PARITY

2 1 FRAME

4 2 NOISE

8 3 HWOVRN 16 4 OVR 32 5 RTSH 64 6 CTSH

128 7 DCAS

SIM983 Scaling Ampliﬁer

3 – 22 Remote Operation

PARITY : Parity error. Set by serial parity mismatch on the incoming data

byte.

FRAME : Framing error. Set when an incoming serial data byte is missing

the STOP bit.

NOISE : Noise error. Set when an incoming serial data byte does not

present a steady logic level during each asynchronous bitperiod window.

HWOVRN : Hardware Overrun. Set when an incoming serial data byte is

lost due to internal processor latency. Causes the input buﬀer to be ﬂushed, and resets the command parser.

OVR : Input buﬀer Overrun. Set when the input buﬀer is overrun by

the incoming data. Causes the input buﬀer to be ﬂushed, and resets the command parser.

RTSH : RTS Holdoﬀ Event. Unused in the SIM983.

CTSH : CTS Holdoﬀ Event. Unused in the SIM983.

DCAS : Device Clear. Indicates that the SIM983 received the Device

Clear signal (an RS–232 hbreaki). Clears the input buﬀer and the output queue, and resets the command parser.

3.5.6 Communication Error Status Enable (CESE)

The CESE acts as a bitwise AND with the CESR register to produce the single-bit CESB message in the Status Byte Register (SB). The

At power-on, this register is cleared.

3.5.7 Overload Status (OLSR)

The Overload Status Register consists of 3 event ﬂags; each of the ﬂags is set by the corresponding overload, and cleared only by read-

ing the register or with the *CLS command. Reading a single bit (with the OLSR? i query) clears only Bit i.

Weight Bit Flag

1 0 Input

2 1 Input + Oﬀset

4 2 Output

8 3 undef (0) 16 4 undef (0) 32 5 undef (0) 64 6 undef (0)

128 7 undef (0)

SIM983 Scaling Ampliﬁer

3.5 Status Model 3 – 23

Input : Input overload. Indicates that |Vin| > 10.0 V (see also Sec-

tion 1.2.4.1).

Input + Oﬀset : Intermediate stage overload. Indicates that |Vin+V

Output : Output overload. Indicates that |V

Reading this register (with the OLSR? query) clears all overload bits

that are set. If the overload condition persists, the bits will remain

cleared until the overload condition ceases and reoccurs. Use OVLD?

to query the current state of the overload.

3.5.8 Overload Status Enable (OLSE)

The OLSE acts as a bitwise AND with the OLSR register to produce the single-bit OLSB message in the Status Byte Register (SB). The

At power-on, this register is cleared.

| > 10.0 V.

out

| > 10.0 V.

ofs

SIM983 Scaling Ampliﬁer

3 – 24 Remote Operation

SIM983 Scaling Ampliﬁer

4 Performance Veriﬁcation

This chapter describes the tests necessary to verify the SIM983 is operating correctly and within speciﬁed calibration.

In This Chapter

4.1 Verifying the DC Accuracy . . . . . . . . . . . . . . 4 – 2

4.2 Verifying AC Performance . . . . . . . . . . . . . . 4 – 4

4.3 Noise Characteristics . . . . . . . . . . . . . . . . . . 4 – 6

4.4 Performance Test Record . . . . . . . . . . . . . . . 4 – 8

4.1.1 Getting ready . . . . . . . . . . . . . . . . . . 4 – 2

4.1.2 Interpreting the accuracy speciﬁcations . . . 4 – 2

4.1.3 Input bias current . . . . . . . . . . . . . . . . 4 – 4

4.2.1 Transfer characteristic . . . . . . . . . . . . . 4 – 4

4.2.2 Step response . . . . . . . . . . . . . . . . . . 4 – 4

4.2.3 Slew rate . . . . . . . . . . . . . . . . . . . . . 4 – 6

4.2.4 Total harmonic distortion . . . . . . . . . . . 4 – 6

4.4.1 DC test . . . . . . . . . . . . . . . . . . . . . . 4 – 8

4.4.2 Noise test . . . . . . . . . . . . . . . . . . . . 4 – 9

4 – 1

4 – 2 Performance Veriﬁcation

4.1 Verifying the DC Accuracy

The gain and the oﬀset of the SIM983 Scaling Ampliﬁer are calibrated at the factory. Besides self-calibration, there are no user-adjustable calibration settings.

4.1.1 Getting ready

To verify the DC performance of the SIM983, one needs a DC signal source (able to output either polarity) and, as a minimum, a voltmeter accurate to ±500 µV or better. Two voltmeters with matched calibration are most convenient, such as two channels of the Stanford Research Systems’ SIM970 Quad DVM. The SIM928 Isolated Voltage Source is recommended as the calibrator; however, the wiper of a potentiometer connected to a power supply can be a simpler if less convenient solution. The DC source must be quiet. If the veriﬁcation is done with only one voltmeter, cables have to be connected and disconnected between measurements, so the voltage source must be stable within the voltmeter’s accuracy. No such stability is required if two voltmeters are used.

1. Warm up the SIM983 for at least 2 hours.

2. If the voltmeter requires a warmup of a certain duration prior to establishing its accuracy speciﬁcations, or an autocalibration, be certain to complete these.

3. Perform an autocalibration of the SIM983 as speciﬁed in Section 2.2.

In order to perform the measurements, connect the output of the voltage source to the input of the ampliﬁer and to Voltmeter 1. Connect the output of the SIM983 to Voltmeter 2. If using only one voltmeter, use it to alternately measure the DC source voltage and the output voltage of the SIM983.

4.1.2 Interpreting the accuracy speciﬁcations

Gain and oﬀset errors speciﬁed in the table on Page vi contribute to the overall output error. The error in V

δV

out

The gain error δG and the oﬀset error δV dependent contributions, mentioned in the speciﬁcation table under “Stability”.

= δG × (Vin+ V

= G × (Vin+ V

out

) + G × δV

ofs

both have temperature-

ofs

) is

ofs

SIM983 Scaling Ampliﬁer

4.1 Verifying the DC Accuracy 4 – 3

4.1.2.1 Error budget

Consider, for example, a measurement with G = +13.30, Vin= 6.192 V, and V

= −5.480 V, performed at a laboratory

ofs

temperature of +28◦C.1The following are the worst-case contributions of the factors speciﬁed in the table on Page vi to the output error:

Speciﬁcation Contribution to Overall Error, V

Gain accuracy, ±0.01 ±0.01 × (6.192 − 5.480) = ±0.0071 Gain stability, (28◦C − 23◦C) × (±10 ppm/◦C) = ±50 × 10 Oﬀset accuracy, ±1 mV ± 200 ppm 13.30 × (±0.001 ± 200 × 10−6× (−5.480)) = ±0.0279 Oﬀset stability,

(28◦C − 23◦C) × (±20 µV/◦C ± 20 ppm/◦C)

= ±100 µV ± 100 × 10

−6

13.30 × (±0.0001 ± 100 × 10−6× (−5.480)) = ±0.0086

Total = ±0.0436

±50 × 10−6× (6.192 − 5.480) = ±0.0000

The output of the instrument is therefore

= 13.30 × (6.192 V − 5.480 V) ± 0.0436 V = (9.47 ± 0.04) V

out

Gain accuracy, ±0.01 ±0.01 × (−3.954 − 5.480) = ±0.0943 Oﬀset accuracy, ±1 mV ± 200 ppm ±0.001 ± 200 × 10−6× (−0.19) × (−3.954 − 5.480) = ±0.0014

4.1.2.2 Recalibration

if the ampliﬁer is performing within its speciﬁcations.

Consider another example, with G = −0.19, Vin= −3.954 V, and V

= −5.480 V, performed at a laboratory temperature of +23◦C.

ofs

For |G| < 1, the speciﬁed oﬀset error term is referenced to the output, according to Note 4 on Page vii. The worst-case error budget is

Speciﬁcation Contribution to Overall Error, V

Total = ±0.0957

The stability terms are zero because the test is taken at the calibration temperature. The output of the SIM983 is therefore

= −0.19 × (−3.954 V − 5.480 V) ± 0.0957 V = (1.79 ± 0.10) V

out

if the unit is working according to the speciﬁcations.

When interpreting the results of a DC performance test of the SIM983, always account for the voltmeter accuracy speciﬁcations.

If the module fails its DC accuracy speciﬁcations, return it to Stanford Research Systems for a new calibration.

SIM983 Scaling Ampliﬁer

Note that the input voltage by itself, or the output voltage by itself, overloads the ampliﬁer at the chosen gain, but their combination does not.

4 – 4 Performance Veriﬁcation

4.1.3 Input bias current

A simple test of the input current can be done by connecting the input of the SIM983 to the input of a voltmeter that has a microvolt range, such as the SIM970. The current will ﬂow through a parallel combination of the 1 MΩ input resistance of the SIM983 and the input resistance of the voltmeter, which is typically 10 MΩ in the SIM970 and is that or greater in other voltmeters. Divide the voltmeter reading by the resistance (e.g. 0.9 MΩ) to obtain the current. A current that exceeds the speciﬁcation in the table on Page vi indicates a damaged front end. The module should then be returned to Stanford Research Systems for repair.

4.2 Verifying AC Performance

Most information about the AC behavior of the SIM983 Scaling Ampliﬁer can be deduced by observing the response of the instrument to a square wave at the input. The equipment required for the test is a function generator with at most 25 ns square-wave rise time, such as the Stanford Research Systems’ DS345, and an oscilloscope with at least 100 MHz bandwidth. An FFT spectrum analyzer, such as the Stanford Research Systems’ SR785, is needed to measure total harmonic distortion and noise.

4.2.1 Transfer characteristic

It is possible to measure the small-signal bandwidth of the ampliﬁer by applying a 100 mV peak-peak sine wave to its input, and increasing the frequency of the applied signal until the output amplitude reduces to −3 dB, i.e.1/ small-signal bandwidth can also be measured from the rise time of the instrument’s response to a small-input step. For example, in Figure 4.1 measure the rise time of the output from 10% to 90%, i.e. −400 mV to +400 mV:

so the small-signal bandwidth

which is consistent with the bandwidth expected from GBP = 3.0 MHz in the speciﬁcation table on Page vi.

4.2.2 Step response

Figures 4.1–4.6 illustrate the typical responses of a SIM983 to steps in the input voltage. Figure 4.2 is for G = 4.00, a value near the

√

2, of its low-frequency value. However, the

= 111 ns,

rise

−3 dB

(G = 1) =

0.35

rise

= 3.1 Mhz,

SIM983 Scaling Ampliﬁer

4.2 Verifying AC Performance 4 – 5

TDS 3034 28 Apr 2006 11:38:08

TDS 3034 28 Apr 2006 11:39:28

TDS 3034 28 Apr 2006 11:40:44

TDS 3034 28 Apr 2006 11:41:34

top end of the range for BWTH = 1. According to the discussion in

Section 5.1.2.5, the ampliﬁer is relatively overcompensated, resulting in an increased settling time. Compare with Figure 4.3, with

G = 10.00 at the low end of the range for BWTH = 3. The ampliﬁer is

relatively undercompensated, and the smaller phase margin results in some overshoot and ringing.

Figure 4.1: Response of the SIM983 to a 1.0 V peak-peak step, G = +1.00, V

= 0.000 V.

ofs

Figure 4.3: Response of the SIM983 to a 1.0 V peak-peak step, G = +10.00, V

= 0.000 V.

ofs

The asymmetrical positive-going and negative-going responses in Figures 4.5 and 4.6 are ultimate artifacts of the single-ended, as opposed to diﬀerential, topology of the input voltage buﬀer (Section 5.1.2.1).

Figure 4.2: Response of the SIM983 to a 1.0 V peak-peak step, G = +4.00, V

= 0.000 V.

ofs

Figure 4.4: Response of the SIM983 to a 1.0 V peak-peak step, G = +19.99, V

= 0.000 V.

ofs

SIM983 Scaling Ampliﬁer

4 – 6 Performance Veriﬁcation

TDS 3034 28 Apr 2006 11:52:30

TDS 3034 28 Apr 2006 11:53:39

Figure 4.5: Response of the SIM983 to a 20 V peak-peak step, G = +1.00, V

= 0.000 V.

ofs

4.2.3 Slew rate

Slew rate information is contained within the large-input, largeoutput step response (Figure 4.5).2After an initial delay, the output rises from −5.4 V to +5.2 V in 120 ns. The slew rate

4.2.4 Total harmonic distortion

Figure 4.7 shows a distortion measurement made on the SR785 FFT Spectrum Analyzer.

4.3 Noise Characteristics

Figure 4.8 shows noise plots of the SIM983 up to f = 100 kHz, measured with an SR785. Note the quite weak dependence of the inputreferenced noise on the gain for |G| ≥ 1. Figure 4.9 shows the time dependence of the output voltage of the SIM983. The 0.17 Hz singlepole high-pass, and 10 Hz eighth-order low-pass ﬁltering was provided by the SIM965 Analog Filter.

Figure 4.6: Response of the SIM983 to a 20 V peak-peak step, G = +0.10, V

5.2 − (−5.4)

SR =

120 × 10

= 88 V/µs.

−9

= 0.000 V.

ofs

The small-input, large-output step response of Figure 4.4 is limited by the 1.15 MHz bandwidth at G = 19.99, so no slew-rate limitation is evident.

SIM983 Scaling Ampliﬁer

4.3 Noise Characteristics 4 – 7

0 2000 4000 6000 8000 10000 12000

-6

-5

-4

-3

-2

-1

Frequency (Hz)

Voltage Response (V rms)

100

1000

Frequency (Hz)

Voltage Noise (nV/√ Hz)

G = +1.00

G = +19.99 RTI

G = +0.10 RTO

TDS 3034 28 Apr 2006 14:53:41

Figure 4.7: Response spectrum of the SIM983 at G = +1.00 to a 1.0 kHz,

1.0 V rms sine wave, showing harmonic artifacts at < 1 × 10−5of the principal. The total THD for 10 harmonics is −96 dB, as measured by an SR785. The THD does not degrade with higher gain, or larger input signal, up to the overload limits of the SIM983.

Figure 4.8: Noise of the SIM983, referenced to the input for |G| ≥ 1.

SIM983 Scaling Ampliﬁer

Figure 4.9: 0.1 Hz to 10Hz noise of the SIM983, G = +19.99, additional gain of 50.

4 – 8 Performance Veriﬁcation

4.4 Performance Test Record

4.4.1 DC test

Serial number

Lab temperature (◦C) =

G V

ofs

(V) (V) (V) (Vin+ V

out

G × Error Gain Gain Oﬀset Oﬀset Cal

) (V) accuracy stability accuracy stability within

ofs

(V) error (V) error (V) error (V) error (V) spec?

SIM983 Scaling Ampliﬁer

4.4 Performance Test Record 4 – 9

4.4.2 Noise test

Serial number

Input bias current (pA) =

Noise volage, nV/√Hz :

G = −0.10 G = +0.10 G = −1.00 G = +1.00 G = −19.99 G = +19.99

f = 1 kHz

f = 10 kHz

SIM983 Scaling Ampliﬁer

4 – 10 Performance Veriﬁcation

SIM983 Scaling Ampliﬁer

5 Circuit Description

In This Chapter

This chapter presents a brief description of the SIM983 circuit design. A complete parts list and circuit schematics are included.

5.1 Circuit Discussion . . . . . . . . . . . . . . . . . . . 5 – 2

5.1.1 Microcontroller interface . . . . . . . . . . . . 5 – 2

5.1.2 The ampliﬁer . . . . . . . . . . . . . . . . . . 5 – 2

5.1.3 Front panel . . . . . . . . . . . . . . . . . . . 5 – 6

5.2 Parts List . . . . . . . . . . . . . . . . . . . . . . . . . 5 – 6

5.3 Schematic Diagrams . . . . . . . . . . . . . . . . . . 5 – 10

5 – 1

5 – 2 Circuit Description

5.1 Circuit Discussion

The following sections correspond to schematic pages at the end of the manual.

5.1.1 Microcontroller interface

The SIM983 is controlled by microcontroller U107.

5.1.1.1 Digital control and clock stopping

A critical aspect of the design is the clock-stop circuitry implemented by U102 and U105. A simple RC oscillator is enabled or disabled at Pin 1 of U105. This pin is driven by synchronizing ﬂip-ﬂop U102B to ensure that no “runt” clock pulses are produced that would violate the minimum clock period of U107. Four separate clock starting signals are combined by U103 and U104, as discussed in Section 2.4.

The fast start time of the RC oscillator ensures that incoming serial data will be correctly decoded by the microcontroller’s UART, even when the clock is started by the serial start bit of the incoming data. When the microcontroller has completed all pending activity, it drives the STOP signal HIGH (Pin 71 of U107), eﬀectively halting its own processor clock. In this way, the SIM983 guarantees that no digital clock artifacts can be generated during quiescent operation.

5.1.1.2 Power and grounds

5.1.2 The ampliﬁer

5.1.2.1 Input voltage buffer

A separate clean +5 V source is provided by voltage regulator U109 to power the analog circuitry of the ampliﬁer. Each point in the circuit that connects to Ground 2 (Section 2.1.2) is separately routed to Pin 8 of interface connector J101, forming a star ground on Layer 3 of the circuit board.

The signal path in the SIM983 Scaling Ampliﬁer consists of ﬁve stages: the high-impedance input voltage buﬀer, the summing ampliﬁer, the voltage inverter, the programmable gain stage, and the passive LRC ﬁlter. Other parts of the ampliﬁer circuit are the precision voltage reference, the oﬀset voltage generator, and the output microvoltmeter, used for autocalibration.

The input buﬀer is a high-impedance (40 pA max bias current), highslew-rate (1200 V/µs typ.), high-speed (105 MHz typ. small-signal

SIM983 Scaling Ampliﬁer

5.1 Circuit Discussion 5 – 3

bandwidth) composite operational ampliﬁer, running at gain 1. Cascoded radiofrequency FET Q201 provides the slew rate and the bandwidth, whereas U201, a precision JFET operational ampliﬁer (opamp), disciplines Q201 to a maximum of 900 µV of oﬀset voltage,

12 µV/◦C maximum oﬀset drift, and 8.5 nV/√Hz typical noise.1The output of the voltage buﬀer is monitored for overload by comparator U213, which trips at the voltage limits speciﬁed in Section 1.2.4.1.

5.1.2.2 Offset voltage generator

The oﬀset voltage is provided by U204, a 16-bit digital-to-analog converter (DAC). Because of the ultralow drift of the DAC and precision resistor network R215, the temperature stability of the generated oﬀset is largely determined by the 5 ppm/◦C typical performance of scaling resistor R217. The integral nonlinearity of U204 puts a 200 ppm limit on the overall accuracy of the instrument’s oﬀset. A second, 12-bit DAC U206 allows for ﬁne tuning of the generated oﬀset, cancelling the contribution of the input oﬀset voltage of U201 and oﬀsets in subsequent stages in order to achieve the speciﬁed accuracy. The oﬀset voltage is ﬁltered by the 6.3 kΩ output resistance of U204 in combination with C206, with f

−3 dB

= 11 Hz.

5.1.2.3 Summing ampliﬁer

The voltages at the outputs of the input buﬀer and the two oﬀsetgenerating DACs are combined by a summing ampliﬁer built around U208A. This low-noise, high-speed op-amp is disciplined by one half of precision op-amp U207, so its input oﬀset contributes negligibly to the overall oﬀset error and the oﬀset drift. However, the input bias current of the op-amp does contribute to the error, and this contribution is partially cancelled by a constant current injected into the summing node through R219. The remaining contribution is calibrated out via U204 and U206.

At this stage, three major contributions to the overall noise of the SIM983 come into play; these contributions are comparable in

magnitude, and add in quadrature. The 1.5 nV/√Hz noise (at 10 kHz) of U208 faces a noise gain of 6 from R216 and R217. The input

buﬀer contributes another 9.5 nV/√Hz. Finally, the Johnson noise of the 2.5 kΩ resistors of R216 and the 604 Ω R217, times the noise gain, yields 16.5 nV/√Hz, referenced to the input. Therefore, the

total noise at the output of this stage is typically 21 nV/√Hz. The input bias current of U208, passing through the feedback portion

The 9.4 nV/√Hz noise at the output of the input voltage buﬀer includes the contribution of the 1 kΩ input protection resistor R203.

SIM983 Scaling Ampliﬁer

5 – 4 Circuit Description

of R216, only generates a contribution of 3 nV/√Hz, insigniﬁcant when added in quadrature.

Scaling resistor network R216 is highly stable, and does not contribute appreciably to the drift of the gain.

5.1.2.4 Voltage inverter

The inverson, if required, is performed by the other half of dual opamp U208. Precision resistor network R222 is connected in such a way that the noise gain of the op-amp is always 2, ensuring stability from oscillation. The Johnson noise of the network contributes to the overall noise of the SIM983, resulting in 22 nV/√Hz (typ., at 10 kHz) at the stage’s output.

Because the inverting stage is not disciplined, its oﬀset contributes to the overall error; this oﬀset typically drifts by 10 µV/◦C, and, combined with the drift of the input voltage buﬀer, this error determines the oﬀset stability of the instrument. The error produced by the input bias current of the op-amp is calibrated out.

5.1.2.5 Gain stage

The output of the summing ampliﬁer is monitored for overload by comparator U214, triggered at the voltage limits discussed in Section 1.2.4.1.

The variable-gain element is one half of high-speed op-amp U211, connected in the inverting conﬁguration. Two matched converters of dual multiplying DAC (MDAC) U210 serve as variable input and feedback resistors for this inverting ampliﬁer:

R(U210B)

|G| =

R(U210A)

When |G| ≤ 1, U210B is set to or near its minimum resistance value of 10 kΩ, and U210A, to an equal or greater resistance. The situation is reversed for |G| > 1. The 12-bit resolution of the MDACs places limitations on the values of achievable gains. The two MDACs track to within 10 ppm/◦C, and this term is the dominant one for the stability of the instrument’s gain.

Similarly to the summing portion of U208, the gain ampliﬁer (U211A) is disciplined by U207B in order to achieve a negligible contribution to the overall oﬀset, oﬀset drift, and noise. However, the error from the input bias current of U211A (which is multiplied by the resistance R(U210B) ) is not negligible.2A ﬁrst-order cancellation of the

The same part as U208 could not be used in place of U211 because the lownoise U208 is not unity-gain stable.

SIM983 Scaling Ampliﬁer

5.1 Circuit Discussion 5 – 5

bias is achieved by mirroring the input current of the second half, U211B, and injecting it into the input node of U211A. The remaining input current produces a drift term that is roughly the same as, or smaller than, the other dominant contributions to the oﬀset stability of the instrument.

This cancellation scheme increases the contribution of the gain stage to the overall noise. The noise current of U211 is multiplied

by R(U210B) and by√2. As R(U210B) increases linearly with the gain for |G| ≥ 1, this terms yields 21 nV/√Hz, referenced to the input.

The remaining noise contribution is from R(U210A) and R(U210B). Their Johnson noise at the output of the stage depends on the gain as

en∝p|G|(1 + |G|),

and for large gains is just the noise of the 10 kΩ resistor R(U210A), referenced to the input. This 13.5 nV/√Hz term adds in quadrature with the 22 nV/√Hz contribution of the earlier three stages, and with the bias-current contribution, to yield 34 nV/√Hz ( f & 10 kHz). At

most frequencies f & 100 Hz, and for |G| ≥ 1, the input-referenced noise of the SIM983 is independent of the gain to within 2 nV/√Hz.

The capacitances of the analog switches3that conﬁgure the variableresistance MDAC add together at the output of the MDAC. This capacitance becomes the input capacitance of the inverting ampliﬁer, and its value places the ultimate limits on the small-signal bandwidth achievable in the gain stage and with it, in the whole instrument. The capacitance together with R(U210A) forms an input pole, so if the gain of the ampliﬁer is not rolled oﬀ with a capacitor in the feedback path, the ampliﬁer will oscillate. The amount of compensation feedback capacitance desired for stability from oscillation increases with decreasing |G|. The compensation network consists of PFETs Q205–Q208, funcioning as switches and chosen for ultralow OFF capacitance, and capacitors C208–C210. One, both, or none of C209 and C210 are inserted into the feedback path for four ranges of the gain, resulting in four possible values of the gain-bandwidth product of the stage (Page vi). With the feedback capacitor selected, the phase margin of the ampliﬁer improves with increasing |G|, and with it the overshoot and ringing in the step response decrease.

Output voltage buﬀer U212 enables the instrument to drive 50 Ω loads. Comparator U215 indicates an overload at the speciﬁed output voltage limits (Section 1.2.4.2).

Internal to the MDAC.

SIM983 Scaling Ampliﬁer

5 – 6 Circuit Description

STANFORD RESEARCH SYSTEMS, INC. SIM983 Scaling Amplifier Circuit Board (1 of 1) Revision D

BILL OF MATERIALS May 5, 2006

Item Qty. Reference Part SRS P/N Manufacturer Manf. P/N

1 2 C101,C102 22µ T 5-00327-030 VISHAY 199D226X9035E6B1 2 10 C103,C110,C111,C205,C221, 10µ T 5-00098-030 VISHAY 199D106X9035D2B1

C222,C223,C224,C225,C226 3 1 C104 330p 5-00381-100 KEMET C1206C331J5GACTM 4 1 C105 9.0--50p 5-00106-090 XICON 24AA024 5 3 C106,C107,C108 1000p 5-00387-100 KEMET C1206C102J1GACTM 6 5 C109,C217,C218,C219,C220 1.0µ T 5-00099-030 VISHAY 199D105X9035A2B1 7 1 C201 2.7p NP0 ±0.25p 5-00630-100 KEMET C1206C279C5GACTM 8 2 C202,C210 3.3p NP0 ±0.25p 5-00357-100 KEMET C1206C339C5GACTM 9 3 C203,C204,C209 1.5p NP0 ±0.25p 5-00353-100 KEMET C1206C159C5GACTM 10 2 C206,C216 2.2µ MPE 5% 5-00584-050 PANASONIC ECQ-E1225JFB 11 2 C207,C213 4.7µ MPE 5% 5-00073-050 XICON 146-250V4.7K 12 1 C208 0.5p NP0 ±0.25p 5-00592-100 AVX 12065A0R5C 13 1 C211 1500p NP0 5% 5-00389-100 KEMET C1206C152J5GACTM 14 2 C212,C214 1.0µ MPE 5% 5-00245-050 WIMA MKS4/1/63/5RM10 15 1 C215 10µ MPE 10% 5-00072-050 PANASONIC ECQ-E1106KF

5.1.2.6 Output ﬁlter

The performance of the passive ﬁlter, composed of L201, R226, R227, and C211, is described on Schematic Page 2. The ﬁlter eliminates the broad-spectrum noise of high-bandwidth ampliﬁers Q201, U208, and U211 beyond a few megahertz, while adding a negligible amount of overshoot in the step response.

5.1.2.7 Output microvoltmeter

The analog-to-digital converter (ADC) used for autocalibration is a part of microcontroller U107. The output signal is ampliﬁed by precision op-amp U217, then shifted by +2.5 V by shunt reference D201 and fed into the ADC.

5.1.3 Front panel

Bright red 7-segment LED displays U302, U304, U306, U307, U309, U311, U313, and U314, and overload LEDs D301 and D302 are driven by shift registers U301, U303, U305, U308, U310, U312, and U315.

5.2 Parts List

SIM983 Scaling Ampliﬁer

5.2 Parts List 5 – 7

Item Qty. Reference Part SRS P/N Manufacturer Manf. P/N

16 43 X101,X102,X103,X104,X105, 0.1µ 5-00299-100 KEMET C1206C104K5RACTM

X106,X107,X108,X109,X110,

X111,X112,X113,X114,X115,

X201,X202,X203,X204,X205,

X206,X207,X208,X209,X210,

X211,X212,X213,X214,X215,

X216,X217,X218,X219,X220,

X221,X301,X302,X303,X304,

X305,X306,X307

17 2 D101,D102 BAT54S 3-00945-143 DIODES INC BAT54S-7 18 1 D201 TL431CDBV 3-01133-123 PHILIPS TL431CD5 19 1 D202 BAV99 3-00896-145 ON SEMI BAV99LT1 20 2 D301,D302 Red 3-00425-060 LITEON LTL-709E

21 1 J101 15 Pin D 1-00367-040 CINCH DAKL-15PATI-E 22 0 J102 Header 0.100" 4×1 no part 23 1 J103 Socket 0.100" 3×2 1-00302-010 SAMTEC CES-103-01-G-D 24 1 J104 Header 0.050" 7×2/Mixed 1-01063-109 SAMTEC FTSH-107-04-L-M-T 25 0 J201,J202,J203 Flying Leads no part 26 1 J301 Socket 0.050" 7×2/SM 1-01064-119 SAMTEC FLE-107-01-G-DV-A

27 3 L101,L102,L103 FR43 bead 6-00174-051 FAIR-RITE 2643666611 28 1 L201 1.2µ 5% 500mA 6-00676-100 API DELEVAN 1210-122J

29 0 MH101,MH102,MH103,MH104 Mounting Hole no part

30 2 Q201,Q202,Q203 MMBF4416 3-01324-152 VISHAY SST4416 31 1 Q204 MMBT2907A 3-00927-150 ON SEMI MMBT2907ALT1 32 4 Q205,Q206,Q207,Q208 MMBF5460 3-01305-152 FSC MMBF5460

33 5 R101,R111,R112,R115,R117 100k 5% 4-01527-100 VENKEL CR1206-8W-104JT 34 1 R102 1.0k 4-01479-100 VENKEL CR1206-8W-102JT 35 1 R103 210 4-01052-110 VENKEL TRN55CF-2100TR 36 1 R104 3.9k 4-01493-100 VENKEL CR1206-8W-392JT 37 1 R105 3.9k×4 D 4-00917-120 BI BCN164A-392-J7 38 3 R106,R261,R314 4.7k 4-01495-100 VENKEL CR1206-8W-472JT 39 1 R107 22k 4-01511-100 VENKEL CR1206-8W-223JT 40 1 R108 10 4-01431-100 VENKEL CR1206-8W-100JT 41 3 R109,R118,R119 270 4-01465-100 VENKEL CR1206-8W-271JT 42 5 R110,R120,R121,R227,R262 100 5% 4-01455-100 VENKEL CR1206-8W-101JT 43 3 R113,R114,R260 10k 4-01503-100 VENKEL CR1206-8W-103JT 44 1 R116 100k×4 D 5% 4-01704-120 CTS 742C083104J 45 1 R122 150 5% 4-01459-110 VISHAY CRCW1206151JRT1 46 1 R123 121 4-01029-110 VENKEL TRN55CF-1210TR 47 1 R124 365 4-01075-110 VENKEL TRN55CF-3650TR

SIM983 Scaling Ampliﬁer

5 – 8 Circuit Description

Item Qty. Reference Part SRS P/N Manufacturer Manf. P/N

48 8 R201,R219,R223,R224,R233, 1.00M 4-01405-110 VENKEL TRN55CF-1004TR

R234,R242,R249 49 2 R202,R203 1.00k 1.0W flameproof 4-00542-000 VISHAY CPF11K0000FKB14 50 2 R204,R205 200 1% 4-01050-110 VENKEL TRN55CF-2000TR 51 1 R206 510 4-01472-100 VENKEL CR1206-8W-511JT 52 8 R207,R210,R211,R212,R239, 1.00k 4-01117-110 VENKEL TRN55CF-1001TR

R246,R253,R258 53 1 R208 280 4-01064-110 VENKEL TRN55CF-2800TR 54 1 R209 4.02k 4-01175-110 VENKEL TRN55CF-4021TR 55 1 R213 909 4-01113-110 VENKEL TRN55CF-9090TR 56 1 R214 14.0k 4-01227-110 VENKEL TRN55CF-1402TR 57 2 R215,R222 1.000k×2 1ppm/K 0.1%rat 4-01738-122 VISHAY MPM2001AT 58 1 R216 2.500k×2 1ppm/K 0.1%rat 4-01721-122 VISHAY MPM5001AW 59 1 R217 604.0 5ppm/K 4-01733-000 VISHAY PTF56604R00BZBF 60 1 R218 523k 4-01378-110 VENKEL TRN55CF-5233TR 61 1 R220 49.9k 4-01280-110 VENKEL TRN55CF-4992TR 62 1 R221 10.0 4-00925-110 VENKEL TRN55CF-10R0TR 63 1 R225 10.0k 4-01213-110 VENKEL TRN55CF-1002TR 64 1 R226 2.00k 4-01146-110 VENKEL TRN55CF-2001TR 65 1 R228 35.7 2W flameproof 4-01735-000 VISHAY CPF235R700FKB14 66 1 R229 5.1 4-01424-100 VENKEL CR1206-8W-5R1JT 67 2 R230,R231 13.3 2W flameproof 4-01736-000 VISHAY CPF213R300FKB14 68 3 R232,R241,R248 365k 4-01363-110 VENKEL TRN55CF-3653TR 69 1 R235 649k 4-01387-110 VENKEL TRN55CF-6493TR 70 3 R236,R243,R250 221k 4-01342-110 VENKEL TRN55CF-2213TR 71 6 R237,R238,R244,R245,R251, 2.4M 4-01560-100 VISHAY CRCW1206245JRT1

R252 72 3 R240,R247,R254 3.01k 4-01163-110 VENKEL TRN55CF-3011TR 73 1 R255 392 4-01078-110 VENKEL TRN55CF-3920TR 74 1 R256 732 4-01104-110 VENKEL TRN55CF-7320TR 75 1 R257 249 4-01059-110 VENKEL TRN55CF-2490TR 76 1 R259 150k 1% 4-01326-110 VENKEL TRN55CF-1503TR 77 13 R301,R302,R303,R304,R305, 4.7k×4 D 4-00911-120 BI BCN164A-472-J7

R306,R307,R308,R309,R310,

R311,R312,R313 78 2 R315,R316 2.2k 4-01487-100 VENKEL CR1206-8W-222JT

79 5 S301,S302,S303,S304,S305 B3F-1052 2-00053-000 OMRON B3F-1052

80 0 TP101 Test Point no part

SIM983 Scaling Ampliﬁer

5.2 Parts List 5 – 9

Item Qty. Reference Part SRS P/N Manufacturer Manf. P/N

81 2 U101,U108 74HC14 3-00662-103 PHILIPS 74HC14D 82 1 U102 74HC74 3-00742-103 TI SN74HC74D 83 2 U103,U104 74HC21 3-01502-103 PHILIPS 74HC21D 84 1 U105 74AC00 3-01405-100 FSC 74AC00SC 85 1 U106 MAX6348 4.4V 3-00903-124 MAXIM MAX6348UR44-T 86 1 U107 68HC912B32 3-01379-114 FREESCALE MC68HC912B32CFU8 87 1 U109 LM317L 3-00096-030 ON SEMI LM317LZ 88 1 U201 AD8510A 3-01318-120 ANALOG AD8510AR 89 2 U202,U203 LM7121 3-01306-120 NSC LM7121IM 90 1 U204 MAX5541C 3-01217-171 MAXIM MAX5541CSA 91 2 U205,U207 OPA2227A 3-01471-120 TI OPA2227UA 92 1 U206 LTC1452C 3-00652-171 LTC LTC1452CS8 93 1 U208 THS4032 3-01219-120 TI THS4032CDGN 94 1 U209 DG419 3-01367-122 VISHAY DG419DY 95 1 U210 AD5415 3-01171-171 ANALOG AD5415YRU 96 1 U211 EL2244 3-01300-120 INTERSIL EL2244CS 97 1 U212 BUF634P 3-01221-120 TI BUF634P 98 3 U213,U214,U215 LM393 3-00728-121 TI LM393D 99 1 U216 MAX6225BC 3-00970-123 MAXIM MAX6225BCSA 100 1 U217 OPA277A 3-01370-120 TI OPA277UA 101 7 U301,U303,U305,U308,U310, 74HC595A 3-00672-103 ON SEMI MC74HC595ADT

U312,U315 102 2 U302,U309 HDSP-A107 3-01424-061 AVAGO HDSP-A107 103 6 U304,U306,U307,U311,U313, HDSP-A101 3-00290-061 AVAGO HDSP-A101

U314

104 5 no designator Button Cap 0-00996-999 OMRON B32-1000 105 4 no designator 4-40x1/4 Pan Phil 0-00187-999 ACF PPM-04C04-0-Z 106 4 no designator #4 Split Washer 0-00096-999 J&M 4NLOCLZ 107 2 no designator 4-40x3/8 Flat Phil 0-00835-999 ACF PUM-04C06-0-Z 108 4 no designator 4-40x1/8 Pan Slot 0-00148-999 ACF SPM-04C02-0-Z 109 4 no designator 4-40x1/8 Pan Phil 0-00515-999 ACF PPM-04C02-0-Z 110 8 no designator 4-40x1/8 Black Flat Phil 0-00371-999 ACF PUM-04C03-0-B 111 6 no designator 1.5" 24AWG Uninsulated 0-00772-999 > > 112 1 no designator 6.5" 22AWG White 0-00436-999 > > 113 1 no designator 6.5" 22AWG Black 0-00268-999 > > 114 1 no designator 7.5" 22AWG Red 0-00154-999 > > 115 1 no designator 7.5" 22AWG Black 0-00161-999 > > 116 1 no designator 3.0" 22AWG Red 0-00006-999 > >

117 2 no designator BNC Insulated 1-00073-256 AMPHENOL 31-10-4052 118 1 no designator BNC 1-00003-256 TYCO 227169-4

119 1 no designator Circuit Board 7-01639-999 FAB SIM983 Circuit Board Rev. D 120 1 no designator Front Panel 7-01603-999 FAB SIM983 Front Panel Rev. B 121 1 no designator Lexan Overlay 7-01605-999 FAB SIM983 Front Lexan Rev. B 122 1 no designator Rear Panel 7-01604-999 FAB SIM983 Rear Panel Rev. A 123 2 no designator Top/Bottom Bracket 7-00933-999 FAB SIM Sglw. Bracket Rev. D 124 2 no designator Module Cover 7-00932-999 FAB SIM Module Cover Rev. C2 125 4 no designator Rubber Foot 0-00188-999 MOUSER 5167-202 126 1 no designator Serial Number Label 9-01545-999 FAB SIM SN Label Rev. A

SIM983 Scaling Ampliﬁer

5 – 10 Circuit Description

5.3 Schematic Diagrams

Circuit schematic diagrams follow this page.

SIM983 Scaling Ampliﬁer

¬DAC_2 Sheet 2

¬DAC_1 Sheet 2

¬DAC_0 Sheet 2

C110

10µ T

U105C

74AC00

D+5V

U105B

D+5V

¬START

The regulator

poisons the circuit

with a noise peak

at ~= 6.0 kHz if

A+5V

R123

121

Vout

ADJ

Vin

U109

LM317L

C109

1.0µ T

R122

150 5%

+15V

C104

74AC00

U105A

U102B

U102A

330p

R103

210

74AC00

R102

1.0k

810

¬Q¬PR

CLK

¬CL

74HC74

¬Q¬PR

CLK

¬CL

74HC74

STOP

not decoupled

R124

365

¬RESET

D+5V

1 2

3 4

5 6

J103

D102

D+5V

C105

9.0--50p

Trim to (5.000 ± 0.020) MHz

CLK

R101

100k

Background Debug

Socket 0.100" 3×2

Header pinout!

BKGD

R108

BAT54S

R107

TP101

3940414243444546181920212223242565432180

PA0

PA1

PA2

PA3

PA4

PA5

PA6

PA7

X104

0.1µ

5960 78

22k

31 47 10

U107

68HC912B32

CLK

D+5V

R106

PB0

VFP

VDDAVSSA VDDX

VDDX VDD VDD

EXTAL

XTAL

¬RESET

PE0/¬XIRQ

3334323738363529282726

¬RESET

4.7k

-RESET

VCC

GND

U106

MAX6348 4.4V

321

U103B

U101D

U101B

74HC14

3 4

U101C

U101A

74HC14

1 2

¬Button polarity

Clock Wake-Up

¬Input OverloadSheet 2

¬DAC_2

¬DAC_0

¬DAC_1

Chip Enables:

PB1

PB2

PB3

PB4

PB5

PB6

PB7

PP0/PW0

PP1/PW1

PE1/¬IRQ

PE2/RW

PE3/¬TAGLO/¬LSTRB

PE4/ECLK

PE5/IPIPE0/MODA

PE6/IPIPE1/MODB

PE7/¬DBE

MODB

BKGD

ECLK

MODA

123

Aux Debug

J102

Header 0.100" 4×1

¬START

U103A

74HC21 1

462

U104A

74HC21

12810

74HC14

9 8

74HC14

5 6

¬RESET

¬Button gain ^

¬TXD

Idles HIGH

¬Output OverloadSheet 2

¬Invert Sheet 2

U105D

R116B100k×4 D 5%

R116C100k×4 D 5%

R116A100k×4 D 5%

R116D100k×4 D 5%

D+5V

2 7

3 6

1 8

4 5

¬LEDs

BW Select 1

BW Select 0

¬Invert

(end Chip Enables)

7917767574737271706162636465666768

PP4

PP5

PP6

PP7

PDLC2

PP3/PW3

PDLC1/DLCTX

PDLC0/DLCRX

PT0/IOC0

PT1/IOC1

PT2/IOC2

PT3/IOC3

PT4/IOC4

789

12131415165152535455565758

¬TXD

¬Output Overload

¬Input Overload

¬Add Overload

U104B

462

D+5V

U101F

U101E

¬Button offset ^

¬Button offset v

PDLC3

PT5/IOC5

PT6/IOC6

74HC21 9

74HC14

13 12

74HC14

11 10

¬Add OverloadSheet 2

PP2/PW2

SMOD/¬TAGHI/BKGD

¬Button gain v

SCK Sheet 2

Data In S heet 2

¬BW Select 0 Sheet 2

BW Select 0 Sheet 2

BW Select 1 Sheet 2

¬BW Select 1 Sheet 2

U108D

74HC14

74AC00

9 8

BW Select 0

BW Select 1

STATUS

STOP

¬RTS

Data In

SCK

¬TXD

¬RXD

¬CTS

PS2

PS3

PDLC4

PDLC5

PDLC6

PS1/TXD

PS6/SCK

PS0/RXD

PS4/SDI/MISO

PS5/SDO/MOSI

PT7/IOC7/PAI

PAD0/AN0

PAD1/AN1

PAD2/AN2

PAD3/AN3

PAD4/AN4

PAD5/AN5

PAD6/AN6

VRH

VRL

¬Button offset v

¬Button offset ^

¬Button gain v

¬Button gain ^

¬Button polarity

D+5V

1 8

2 7

3 6

4 5

D+5V

R104 3.9k

R105A3. 9k×4 D

R105B3. 9k×4 D

R105C3.9k×4 D

R105D3.9k×4 D

12810

GND1

¬Button offset v

¬Button gain v

¬Button offset ^

¬Button gain ^

¬Button polarity

1 2

3 4

5 6

7 8

9 10

11 12

13 14

J104

D+5V

To Front

Panel

PS7/¬CS/¬SS

VSSX

VSS

PAD7/AN7

Output × 151Sheet 2

Header 0.050" 7×2/Mixed

Data In

SCK

¬LEDs

RXD

R120

100 5%

R118

270

U108F

74HC14

¬RTS

U108B

74HC14

3 4

D+5V

R112

100k 5%

R113

R111

100k

R109

U108C

74HC14

VDD

VCC

D+5V

-15V

+15V

L103

X103

0.1µ

C103

10µ T

L102

X102

0.1µ

C102

22µ T

L101

X101

0.1µ

C101

22µ T

GND2

D101

BAT54S

GND Chassis

Part Notes, All Pages:

CTS

R121

100 5%

C108

1000p

C107

1000p

R119

270

U108A

74HC14

R117

100k

¬TXD

U108E

74HC14

11 10

R115

100k 5%

R114

10k

C106

1000p

270

R110

100

FR43 Bead

1 2

FR43 Bead

1 2

FR43 Bead

1 2

GND2

+5V In

-15V In

PS Return

+15V In

+24V In

-5V In

+REFCK 10 MHz

¬REFCK 10 MHz

815714613512411310291

J101

15 Pin D

Unless noted:

Resistors are 5%, 0.12 W, or better, for st andard 5% values.

Resistors are 1%, 0.25 W, or better, metal film, for standard 1% values.

Resistors are 0.1%, 0.25 W, or better, m et al film, if 4 significant digits are given.

Capacitors are 20%, 25 V, or better, ceram i c X7R;

MPE = metallized polyester, T = tantalum.

Inductors are 10%, 100 mA, or better.

Networks: D = dual in-line; tem pco i s matching TCR.

D+5V

D+5VD+5V

D+5V

MH104

MH103

MH102

Mounting Holes

MH101

GND1

CTS

¬STATUS ¬STATUS

Signal GND

RXD

RTS

Chassis GND

TXD

13Thursday, May 04, 2006

SIM983 D

Scaling Amplifier: Micr ocontroller Interface

STANFORD RESEARCH SYSTEMS, INC.

Title

Size Document Number R ev

Date: Sheet

X115

0.1µ

X114

0.1µ

Pin 78

X113

0.1µ

Pin 59Pin 10

X112

0.1µ

Pin 47

Pin 31

X111

0.1µ U107 bypass U108 bypass

X110

0.1µ

X109

0.1µ U105 bypassU102 bypass

C111

10µ T

U104 bypass

X108

0.1µ

U103 bypass

X107

0.1µ

X106

0.1µ

U101 bypass

X105

0.1µ

GND

GND Chassis

D D

C C

B B

A A

U217B

OPA277A

GND2

V+

V--

X221

0.1µ

-15V

X220

0.1µ

U215C

LM393

V--

V+

-15V

U214C

LM393

V--

V+

-15V

U213C

LM393

V--

V+

-15V

U211C

EL2244

V+

V--

+15V

-15V-15V

X216

0.1µ

U208C

THS4032

V+

V--

+15V

X214

0.1µ

-15V-15V

C223

10µ T

U207C

OPA2227A

V--

V+

X212

0.1µ

U205C

OPA2227A

V--

V+

+15V +15V

X210

0.1µ

C221

10µ T

U203B

LM7121

V+

V--

+15V

X208

0.1µ

-15V

C219

1.0µ T

U202B

LM7121

V+

V--

X206

0.1µ

-15V

C217

1.0µ T

U201B

AD8510A

V+

V--

+15V +15V

-15V

X204

0.1µ

A A

U212B

BUF634P

V+

V--

J203

J202

¬Output Overload Sheet 1

¬Input Overload Sheet 1

Output × 151 Sheet 1

¬Add Overload Sheet 1

C209

1.5p

NP0 ±0.25p

C208

0.5p

NP0 ±0.25p

Q205

MMBF5460

BW Select 0

X203

0.1µ VDDGND

169

A+5V

SDIN SDO

U210C

AD5415

12 1311101514

A+5V

Data InSheet 1

Data In

SCKSheet 1

¬DAC_0Sheet 1

¬DAC_1Sheet 1

¬DAC_2Sheet 1

¬InvertSheet 1

BW Select 0Sheet 1

¬BW Select 0Sheet 1

BW Select 1Sheet 1

¬BW Select 1Sheet 1

R213

909

+15V

R214

213

R208

280

Vin + 4.0 V

Q204

MMBT2907A

«-- 5 mA

Q203

MMBF4416

BNC Front Output

R230

13.32 W

LCR filter (into

1 MOhm user):

3.5% overshoot

No gain peaking

Output filter

C210

3.3p

NP0 ±0.25p

Q207

MMBF5460

¬BW Select 0

Q206

MMBF5460

BW Select 1

SCLK

¬LDAC

¬CLR

¬SYNC

¬DAC_2

SCK

14.0k

R209

4.02k

C202

3.3p

R206

510

Q201

MMBF4416

R202

1.00k

flameproof

1.0 W

Input buffer

D D

BNC Rear Output

GND Chassis

R231

13.32 W

flameproof

57 ns delay

at 1 MHz

93 ns rise time

R223

flameproof

500 mA5%

C211

1500p

NP0 5%

R229

L201 1.2µ

10% to 90%

Eq. noise BW

= 4.1 MHz

R228

Q208

MMBF5460

¬BW Select 1

1.00M 6

5.1

35.7 2 W

flameproof

U212A

201918

R2B

VrefB

R2_3B

R1B

VFBB

IO1B

IO2B

U210B

AD5415

R224

1.00M

U211B

EL2244

3 4

U210A

AD5415

BUF634P

3 6

R3B

R227

100 5%

GND2

U211A

EL2244

R226

2.00k

R225

10.0k

U207B

OPA2227A

GND2

IO1A

IO2A

VFBA

R1A

R2A

R2_3A

R3A

VrefA

567

Variable gain

U208B

THS4032

U209A

DG419

R222 1.000k×2

268

¬Invert

Invert (or not)Add the offset

R211

1.00k

R210

1.00k

U202A

LM7121

NP0 ±0.25p

~= Vin

R204

200 1%

Q202

MMBF4416

1 ppm/K 0.1% ratio

GND2

U208A

THS4032

R220

49.9k

R216

2.500k×2

1 ppm/K

0.1% ratio

U203A

LM7121

R212

C203

1.5p

NP0 ±0.25p

-15V

R205

200 1%

1.00k

C201

2.7p

NP0 ±0.25p

R203

1.00k

1.0 W

J201

BNC Input

C C

+15V

X218

0.1µ

C225

10µ T

GND2's form

a star-ground

connection to

a single point

located at the

PS Return pin

GND2

A+5V A+5V A+5V

R221

10.0 GND2

U207A

OPA2227A

Overload

GND2

C204

1.5p

NP0 ±0.25p

R207

1.00k

U201A

AD8510A

flameproof

R201

1.00M

GND2

X219

0.1µ

R262

100

-15V

C226

10µ T

of J101

¬Output Overload

R253

1.00k

R251

R246

1.00k

R244

R239

1.00k

R237

R254

3.01k

2.4M 3

¬Add Overload

R247

3.01k

2.4M 3

¬Input Overload

R240

3.01k

2.4M 3

detection

C205

10µ T

X201

0.1µ

A+5V

U204

MAX5541C

Coarse offset

Auto

U215A

LM393

R250

U214A

LM393

R243

U213A

LM393

R236

R217

604.0

U205B

OPA2227A

VDD

REF

345

+2.500 V

offset

D202

BAV99

D+5V

R261

4.7k

+15V

R260

10k

U215B

R252

221k

+15V+15V

R245

221k

R238

221k

+15V

5 ppm/K

OUT

SCLK

DIN

Data In

¬DAC_0

SCK

LM393

2.4M 5

R248

365k

R249

U214B

LM393

2.4M 5

--10.4 V/--9.9 V --10.4 V/--9.9 V

+10.4 V/+9.9 V +10.4 V/+9.9 V

R242

R241

365k

U213B

LM393

2.4M 5

+10.4 V/+9.9 V

--10.4 V/--9.9 V

R235

R234

1.00M

Thresholds:

R232

365k

R233

C207

4.7µ MPE

GND2

C206

2.2µ MPE

AGND

DGND

¬CS

B B

Output × 151

D201

TL431CDBV

U217A

OPA277A

R259

150k

R258

+15V

C215

Low-noise

A+5V

10µ MPE 10%

reference

+2.500 V

Butterworth;

X202

0.1µ

A+5V

C216

2.2µ MPE 5%

f_{-3dB} = 100 Hz

15 nV/VHz

+15V

U216

U206

LTC1452C

1.00M

-15V

649k

1.00M

R215 1.000k×2

1 ppm/K 0.1% rat i o

Fine offset

1.00k

V+

R257

249

R256

732

R255

392

above 100 Hz

OUT

MAX6225BC

R218

523k

0..+24 mV offset trim

range with 6 µV

resolution

VCCGND

REF

631

+2.500 V

+15V

GND2

+15V

-15V

U209B

DG419

V--

GND

U205A

OPA2227A

C214

1.0µ MPE

C213

4.7µ MPE

TRIM

GND

C212

1.0µ MPE

R219

1.00M

+2.500 V

VOUTDIN

¬CS/LD

CLK

DOUT

¬DAC_1

SCK

Data In

GND2

STANFORD RESEARCH SYSTEMS, INC.

23Thursday, May 04, 2006

SIM983 D

Scaling Amplifier: Of fset and Gain

Title

Size Document Number R ev

Date: Sheet

X217

0.1µ

X215

0.1µ

C224

10µ T

X213

0.1µ

X211

0.1µ

C222

10µ T

X209

0.1µ

C220

1.0µ T

X207

0.1µ

C218

1.0µ T

X205

0.1µ

OUTPUT

OVLD

D302

Red

R316

D+5V

INPUT

OVLD

D301

D+5V

U307

HDSP-A101

R305D 4.7k×4 D

R306A 4.7k×4 D

R307B 4.7k×4 D

R307A 4.7k×4 D

R306B 4.7k×4 D

R306C 4.7k×4 D

R306D 4.7k×4 D

D+5V

U314

HDSP-A101

2.2k

R315

2.2k

Red

1512345679

X307

0.1µ

D+5V

U315

R313D

4.7k×4 D

R314

4.7k

dp g f

e d

c b

4 5

7 3 2 4 5 8 9 10

D+5V

VCCGND

168

SCK

¬SCLR

RCK

¬G

1411101213

74HC595A

S. CLK

¬LED

QH'

R312C 4.7k×4 D

R312D 4.7k×4 D

R313A 4.7k×4 D

R313B 4.7k×4 D

STANFORD RESEARCH SYSTEMS, INC.

R313C 4.7k×4 D

33Thursday, May 04, 2006

SIM983 D

Scaling Amplifier: F r ont Panel

Title

Size Document Number R ev

Date: Sheet

U306

HDSP-A101

D+5V D+5V

U304

HDSP-A101

D+5V

PLUS

Gain

U302

HDSP-A107

R303D

4.7k×4 D 4 5

R302A 4.7k×4 D

R302B 4.7k×4 D

R302C 4.7k×4 D36R303A 4.7k×4 D

MINUS

PLUS

MINUS

X301

0.1µ

D+5V

R302D 4.7k×4 D

R301A 4.7k×4 D

R301B 4.7k×4 D

R301C 4.7k×4 D

R301D 4.7k×4 D

1512345679

VCCGND

168

SCK

¬SCLR

RCK

1411101213

U301

74HC595A

D+5V

X302

0.1µ

D+5V

QH'

¬G

R305A 4.7k×4 D

R304D 4.7k×4 D

R304B 4.7k×4 D27R304A 4.7k×4 D

R304C 4.7k×4 D

R303B 4.7k×4 D

R303C 4.7k×4 D

1512345679

VCCGND

168

SCK

¬SCLR

RCK

1411101213

U303

74HC595A

D+5V

¬LED

S. CLK

R305B 4.7k×4 D

¬G

X303

D+5V

QH'

R305C 4.7k×4 D

1512345679

0.1µ VCCGND

168

SCK

1411101213

U305

74HC595A

D+5V

S. CLK

QH'

¬SCLR

RCK

¬G

¬LED

D+5V

U313

HDSP-A101

D+5V

U311

HDSP-A101

D+5V

PLUS

Input

Offset

U309

HDSP-A107

R309B 4.7k×4 D

R309C 4.7k×4 D

R308D 4.7k×4 D 7 3 2 4 5 8 9 10

R308B 4.7k×4 D

R308A 4.7k×4 D

R307C 4.7k×4 D

R307D 4.7k×4 D

R308C 4.7k×4 D

7 3

2 8

1512345679

VCCGND

168

SCK

¬SCLR

1411101213

U308

74HC595A

D+5V

R309A 4.7k×4 D

X305

0.1µ

D+5V

U310

D+5V

QH'

RCK

¬G

dp g f

e d

c b

dp MINUS

PLUS c

MINUS

X304

0.1µ

D+5V

R311C 4.7k×4 D36R311A 4.7k×4 D

R310D 4.7k×4 D

R311B 4.7k×4 D

R310B 4.7k×4 D

R310C 4.7k×4 D

R309D 4.7k×4 D

R310A 4.7k×4 D

1512345679

VCCGND

168

SCK

¬SCLR

RCK

¬G

1411101213

74HC595A

¬LED

S. CLK

X306

D+5V

QH'

R311D 4.7k×4 D

R312B 4.7k×4 D

R312A 4.7k×4 D

1512345679

0.1µ VCCGND

168

SCK

1411101213

U312

74HC595A

D+5V

S. CLK

¬SCLR

RCK

¬G

¬LED

QH'

Data

¬LED

S. CLK

D+5V

135791113

J301

246

GND1

¬Butt polarity

From Digital

Board

S301

B3F-1052

S302

S303

B3F-1052

polarity

gain

D D

Socket 0.050" 7×2/SM

101214

¬Butt offset ^

¬Butt gain v

¬Butt offset v

¬Butt gain ^

S304

B3F-1052

S305

B3F-1052

gain

offset

C C

B B

A A

Appendix A Index

¬STATUS signal, 1 – 2, 1 – 7, 3 – 12, 13, 3 – 20 hbreaki signal, see Device Clear

Accuracy, iii, 4 – 2

gain, see Gain, accuracy oﬀset, see Oﬀset, accuracy verifying at DC, 4 – 2, 4 – 8

Autocalibration, vii, 1 – 2, 2 – 2, 3, 3 – 11, 3 –

13, 3 – 17, 3 – 21, 4 – 2, 5 – 2, 5 – 6

Bandwidth, vi, 1 – 2, 2 – 3, 3 – 6, 3 – 10, 11, 4 –

4, 5, 5 – 2, 5 – 5

default, 1 – 6, 3 – 11, 3 – 14 Baud rate, 1 – 9, 3 – 6 Bias current, vi, 4 – 3, 5 – 2 Block diagram, 1 – 2 BNC, iii, vi, vii, 2 – 2 Buﬀer

input, 3 – 6, 3 – 20–22

overﬂow, 3 – 6, 3 – 22 voltage, see Input, voltage buﬀer

output, see Output queue

voltage, see Output, voltage buﬀer

Button, 3 – 11, 3 – 13, 3 – 21

[gain], 1 – 3, 2 – 3, 3 – 13

[oﬀset], 1 – 4, 3 – 13

[polarity], 1 – 3, 4, 2 – 3, 3 – 13

Calibration, see Factory calibration Circuit schematics, see Schematic diagrams Clock stopping, 1 – 2, 2 – 4, 3 – 10, 3 – 14, 5 – 2 Command

error, 3 – 16, 3 – 21

parameters, 3 – 7, 3 – 16

separator, 3 – 7

terminator, 3 – 6, 7, 3 – 14, 3 – 17 Compensation, 2 – 3, 4 – 4, 5 – 5 Console mode, 3 – 6, 3 – 14, 15

DB–15, 1 – 7, 8, 2 – 2 DB–9

female, 1 – 8

male, 1 – 8

Default conﬁguration, see Reset Device Clear, 3 – 6, 3 – 15, 3 – 17, 3 – 22 Device error, 3 – 16, 3 – 21 Dimensions, vii Distortion, see Total harmonic distortion DS345, 4 – 4

Error

budget, 4 – 2 command, see Command, error

Execution error, 3 – 15, 3 – 21

Factory calibration, 4 – 2, 3 Firmware revision, 3 – 15 Flow control, 1 – 9, 3 – 6, 3 – 17 Front panel, 1 – 2, 3, 2 – 3, 4, 3 – 11

operation, 1 – 3

Full duplex, see Console mode

Gain, iii, vi, 1 – 2, 3, 1 – 6, 2 – 2, 3, 3 – 6, 3 – 10,

11, 5 – 4

accuracy, vi, 2 – 3, 4 – 3 button, see Button, [gain] default, 1 – 4, 1 – 6, 3 – 10, 3 – 14 polarity, see Polarity resetting, 1 – 4, 3 – 13 resolution, vi, 1 – 3, 5 – 4 stability, vi, 4 – 3, 5 – 4

Gain-bandwidth product, vi, vii, 1 – 2, 2 – 3,

3 – 11, 4 – 4, 5 – 5 Gain stage, 2 – 3, 5 – 2, 5 – 4 General information, iii Ground, 1 – 7, 8, 2 – 2, 5 – 2

analog, 1 – 8, 2 – 2, 5 – 2 chassis, 1 – 7, 8, 2 – 2 Earth, 2 – 2 power, 1 – 8, 2 – 2 star, 5 – 2

Help, 3 – 9

A – 1

A – 2 Index

Input

capacitance, vi connector, vi, 2 – 2 coupling, vi overload, see Overload, input resistance, vi, 4 – 3 voltage, iii, 1 – 8

limits, vi, vii, 1 – 5, 5 – 2, 5 – 4

voltage buﬀer, 4 – 5, 5 – 2

Interface

direct, 1 – 7

cable, 1 – 8

remote, see Remote interface SIM, see SIM interface

Inverter, 5 – 2, 5 – 4

Mainframe, see SIM900 Microcontroller, 5 – 2

Noise, vi, 4 – 6, 5 – 3–5

dependence on gain, 4 – 6, 5 – 5

verifying, 4 – 6, 4 – 8 Non-volatile settings, 1 – 6, 3 – 6 Notation, v, 3 – 6, 3 – 8 Null modem, 1 – 8

Oﬀset, iii, vi, 1 – 2–4, 1 – 6, 3 – 6, 3 – 10, 5 – 3

accuracy, vi, 1 – 2, 1 – 4, 2 – 2, 4 – 3, 5 – 3

button, see Button, [oﬀset]

default, 1 – 4, 1 – 6, 3 – 10, 3 – 14

resetting, 1 – 4, 3 – 13

resolution, vi, 1 – 4

settling time, vi, 5 – 3

stability, vi, 4 – 3, 5 – 2–4

voltage limits, vi, 1 – 4 Oﬀset generator, 5 – 2, 3 Output

connector

front, vi, 2 – 2

rear, vi, 2 – 2 current, vi, 1 – 2, 2 – 2 ﬁlter, 5 – 2, 5 – 5 maximum load, 1 – 2, 2 – 2, 5 – 5 overload, see Overload, output resistance, vi, 2 – 2 voltage, iii, 1 – 8

limits, vi, 1 – 5, 2 – 3, 5 – 5

maximum undistorted sine wave, 1 – 2,

2 – 3

voltage buﬀer, 5 – 5 Output queue, 3 – 6, 3 – 15, 3 – 21, 22 Overload, 1 – 2, 1 – 4, 2 – 4, 3 – 14, 4 – 2

input, vii, 1 – 2, 1 – 5, 3 – 14, 3 – 22, 5 – 2

OVLD indicator, 1 – 2, 1 – 5, 5 – 6

input plus oﬀset, vii, 1 – 5, 3 – 14, 3 – 23,

5 – 4

output, vii, 1 – 2, 1 – 5, 3 – 14, 3 – 23, 5 – 5

OVLD indicator, 1 – 2, 1 – 5, 5 – 6

Overshoot, 4 – 4, 5 – 5

Parity, 1 – 9, 3 – 6, 3 – 17, 3 – 21 Parts, 5 – 6 Polarity, vi, 1 – 2–4

button, see Button, [polarity] Power

analog, 5 – 2

ground, see Ground, power

requirements, vi, 1 – 7, 8 Power-on, 1 – 6, 2 – 4, 3 – 6, 3 – 13, 3 – 15, 3 –

17, 3 – 20–23

Preparation for use, iii

Query command, 3 – 7, 3 – 16, 3 – 20

Rear panel, 1 – 2, 3 Registers, see Status, registers Remote interface, vii, 1 – 2, 1 – 6, 2 – 4, 3 – 1,

3 – 6, 3 – 9, 3 – 14

data format, 3 – 10, 11 Reset, 1 – 6, 2 – 3, 3 – 13–15, 3 – 17 Rise time, 4 – 4 RS–232, 1 – 2, 1 – 8, 3 – 6, 3 – 17, 3 – 21, 22, 5 –

settings, 1 – 9, 3 – 17

Safety, iii Schematic diagrams, 5 – 9 Self-test, 3 – 15 Serial interface, see RS–232 Serial number, 3 – 15 Service, iii, 4 – 3 Set command, 3 – 7, 3 – 16 Settling time, see Bandwidth

oﬀset, see Oﬀset, settling time

SIM983 Scaling Ampliﬁer

Index A – 3

SIM900, iii, 1 – 2, 1 – 7, 8, 2 – 2, 3 – 6 SIM928, 4 – 2 SIM965, 4 – 6 SIM970, 4 – 2, 3 SIM interface, vii, 1 – 7, 3 – 20

connector, 1 – 7, 2 – 2, 5 – 2 Slew rate, vi, 2 – 3, 4 – 5, 5 – 2 Speciﬁcations, vi SR785, 4 – 4, 4 – 6 Stability

gain, see Gain, stability

oﬀset, see Oﬀset, stability Status, 3 – 11, 3 – 19

registers, 3 – 11, 3 – 19

CESE, 3 – 12, 3 – 22 CESR, 3 – 6, 3 – 12, 3 – 20–22 ESE, 3 – 12, 3 – 14, 3 – 21 ESR, 3 – 6, 3 – 12, 3 – 15, 3 – 20 OLSB, 3 – 20 OLSE, 3 – 13, 14, 3 – 23 OLSR, 3 – 13, 14, 3 – 22, 23 SB, 3 – 12, 3 – 20–23

SRE, 3 – 12, 3 – 14, 3 – 20 Step response, 4 – 4, 5, 5 – 5 Sticky bits, 3 – 19, 20 Summing ampliﬁer, 5 – 2, 3

Temperature, vi, 2 – 2, 4 – 2 Token, 3 – 7, 3 – 15, 16

mode, 3 – 14, 3 – 17

Total harmonic distortion (THD), vi, 4 – 6

Warmup, vii, 2 – 2, 4 – 2 Weight, vii

SIM983 Scaling Ampliﬁer

Stanford Research Systems SIM983 Operation And Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual