Stanford Research Systems SIM960 Operator Manual

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Operation and Service Manual

Stanford Research Systems

Analog PID Controller

SIM960

Revision 2.3 • October 10, 2013

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.

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 9-01558-903

SIM960 Analog PID Controller

Contents

General Information iii

Safety and Precautions for Use . . . . . . . . . . . . . . . . iii

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

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

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

1 Getting Started 1 – 1

1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2

1.2 Front Panel Operation . . . . . . . . . . . . . . . . . . 1 – 2

1.3 Rear Panel Monitoring . . . . . . . . . . . . . . . . . . 1–7

1.4 SIM Interface . . . . . . . . . . . . . . . . . . . . . . . . 1 – 8

2 Advanced Topics 2 – 1

2.1 PID Tuning Basics . . . . . . . . . . . . . . . . . . . . . 2 – 2

2.2 Ziegler-Nichols’ Tuning . . . . . . . . . . . . . . . . . 2–5

2.3 Anti-Windup and Conditional Integration . . . . . . . 2–7

2.4 Bumpless Transfer . . . . . . . . . . . . . . . . . . . . . 2 – 8

3 Remote Operation 3 – 1

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

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

3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3–7

3.4 Commands . . . . . . . . . . . . . . . . . . . . . . . . . 3–8

3.5 Status Model . . . . . . . . . . . . . . . . . . . . . . . . 3–25

4 Performance Tests 4 – 1

4.1 Getting Ready . . . . . . . . . . . . . . . . . . . . . . . 4 – 2

4.2 Performance Tests . . . . . . . . . . . . . . . . . . . . . 4–2

4.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . 4 – 6

5 Circuitry 5 – 1

5.1 Circuit Descriptions . . . . . . . . . . . . . . . . . . . . 5 – 2

5.2 Parts Lists . . . . . . . . . . . . . . . . . . . . . . . . . 5 – 4

5.3 Schematic Diagrams . . . . . . . . . . . . . . . . . . . 5 – 7

ii Contents

SIM960 Analog PID Controller

General Information

Safety and Precautions for Use

Because of the variety of uses for the SIM960, those responsible for the application and use of this control equipment must satisfy themselves that all necessary steps have been taken to assure that each application and use meets all performance and safety requirements, including any applicable laws, regulations, codes and standards.

Service

WARNING

The SIM960 is not designed, intended, or sold for use in hazardous environments requiring fail-safe operation, including without limitation, operation of nuclear facilities, aircraft or spacecraft control systems, and life support or weapons systems. The user must assure that any failure or misapplication of the SIM960 cannot lead to a consequential failure of any interconnected equipment that could lead to loss of life or limb, or property damage.

The illustrations, charts, and discussions shown in this manual are intended solely for purposes of example. Since there are many variables and requirements associated with any particular control application, Stanford Research Systems does not assume responsibility or liability for actual use based upon the examples shown in this publication.

Do not install substitute parts or perform any unauthorized modiﬁcations to this instrument.

The SIM960 is a double-wide module designed to be used inside the SIM900 Mainframe. Do not turn on the power to the Mainframe or apply voltage inputs to the module until the module is completely inserted into the mainframe and locked in place. Do not exceed ±18 V at any input or output connector.

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

SIM960 Analog PID Controller

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 [Button]; [Adjust ] is shorthand for “[Adjust ] & [Adjust ]”.

• Front-panel indicators are set as Overload.

• Remote command names are set as *IDN?.

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

Remote command examples will all be set in monospaced font. In these examples, data sent by the host computer to the SIM960 are set as straight teletype font, while responses received by the host computer from the SIM960 are set as slanted teletype font.

SIM960 Analog PID Controller

vi General Information

Speciﬁcations

Performance Characteristics

Min Typ Max Units

Ampliﬁer Settings Control type Analog, PID+Oﬀset

Input Range −10 +10 V common mode

−1 +1 V diﬀerential

Proportional gain 10

Integral gain 10

eﬀ. time const. 2 ×10

Derivative gain 10

−1

−2

−6

Oﬀset −10 +10 V

resolution 1 mV

Ampliﬁer Performance Bandwidth 100 kHz

Propagation delay 1 µs

Noise (f > 20 Hz) 8 nV/√Hz, RTI

Output Range −10 +10 V

Conﬁguration Parameter control Digital

Parameter accuracy 1 %

Stability 200 ppm/◦C

Display Resolution 4 digits

V/V

5 ×1051/s

10 s

Inputs Measure BNC, 1 MΩ, ±10 V range

Setpoint Generator Setting −10 +10 V

Operating Temperature [14] 0 40

General Characteristics

Ext. Setpoint BNC, 1 MΩ, ±10 V range

resolution 1 mV

Ramp Rate 10

−3

V/s

Noise (f > 100 Hz) 20 nV/√Hz, RTI

◦

Power ±15, +5 V DC

Supply current 150 (±15 V), 80 (+5 V) mA

Number of inputs 2

Interface Serial (RS-232) through SIM interface

Connectors BNC (3 front, 2 rear); DB–15 (male) SIM interface

Weight 2.1 lbs

Dimensions 3.000W ×3.600H ×7.000D

SIM960 Analog PID Controller

1 Getting Started

In This Chapter

This chapter gives you the necessary information to get started quickly with your SIM960 Analog PID Controller.

1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 – 2

1.2 Front Panel Operation . . . . . . . . . . . . . . . . . . 1 – 2

1.2.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . 1 – 4

1.2.2 Ramping . . . . . . . . . . . . . . . . . . . . . . 1 – 5

1.2.3 Connections . . . . . . . . . . . . . . . . . . . . 1 – 5

1.2.4 Bar displays . . . . . . . . . . . . . . . . . . . . 1 – 6

1.2.5 Restoring the default conﬁguration . . . . . . 1 – 6

1.3 Rear Panel Monitoring . . . . . . . . . . . . . . . . . . 1 – 7

1.3.1 Error Monitor . . . . . . . . . . . . . . . . . . . 1 – 7

1.3.2 Input Setpoint Monitor . . . . . . . . . . . . . 1 – 7

1.4 SIM Interface . . . . . . . . . . . . . . . . . . . . . . . 1 – 8

1.4.1 SIM interface connector . . . . . . . . . . . . . 1–8

1.4.2 Direct interfacing . . . . . . . . . . . . . . . . . 1 – 8

1 – 1

1 – 2 Getting Started

1.1 General

The SIM960 is designed to maintain stability in systems requiring low noise and wide bandwidth. The controller design consists of a front end diﬀerential input ampliﬁer, followed by an integrator and a diﬀerentiator, arranged in what is known as the “ideal” PID topology. The input ampliﬁer (the “error ampliﬁer”) diﬀerences the the two single ended inputs, Setpoint and Measure , and multiplies the resulting error signal (ε) by the proportional gain. The ampliﬁed error is then passed to three parallel control paths:

1. The proportional path, no change is made to the signal.

2. The integral path with gain I.

3. The derivative path gain D.

These three signals can be independently selected to combine at a summing ampliﬁer, which is then buﬀered to the output. A constant oﬀset can also be added, which can be useful in applications that do not use the I term. Mathematically, the behavior is

where the three terms within the braces, and Oﬀset, can be independently enabled or zeroed.

For internal stability, the actual diﬀerentiator is “rolled oﬀ” to limit the derivative gain to +40 dB.

The output circuitry includes a soft limiter that turns on when the output exceeds user speciﬁed upper and lower limits and clamps the output to the limit level. The output bar display on the right side of the front panel has red LEDs at each end to indicate when the output is being limited.

1.2 Front Panel Operation

This section discusses the essentials of operating the SIM960 locally, from the front panel. See Chapter 3 for remote operation.

ε ≡ Setpoint − Measure (1.1)

)

Output = P ×(ε + IZε dt + D

• Press [Select] to choose which conﬁguration parameter to view

in the numerical display. The indicator to the left of each descriptor shows which parameter is displayed. When Shift is highlighted, pressing [Select] steps the parameter selection backwards.

dε

+ Oﬀset (1.2)

SIM960 Analog PID Controller

1.2 Front Panel Operation 1 – 3

Figure 1.1: The SIM960 front panel.

• The P, I, D, Oﬀset, and SP Ramp parameters may be enabled/disabled with [On/Oﬀ]. Each of these parameters has an additional indicator to the right of the descriptor to indicate the on/oﬀ status.

• The Limits parameter has two sublevels: upper and lower limit.

• The Setpoint , Measure, P × ε, and Output values are displayonly. All the other values can be changed using the [ ] buttons; the digit selected for adjustment is indicated by its ﬂashing brightness. Change the digit selection while Shift is highlighted ([ ]).

• There are two formats for the numeric display: Exponential, and ﬁxed decimal. The format used for a particular parameter depends on its range. Parameters P, I, D and SP Ramp (rate) vary by several orders of magnitude and are therefore displayed in exponential format, while all other parameters range from −10 V to +10 V and are displayed in ﬁxed decimal format.

SIM960 Analog PID Controller

• For exponential format, themantissa may bechanged using the up/down arrow buttons. The active digit maybe selected using the left/right buttons (= shift, followed by up/down button).

1 – 4 Getting Started

The right-most digit (after ) is the power of ten exponent. For example, the display = 1200.

• The P parameter has a selectable “±” indicator before the mantissa.This allows the polarity of the controller to be tog-Polarity =⇒ gled by the user. All other exponentially displayed parameters are unipolar, so no sign is displayed for these parameters.

• In ﬁxed decimal format a value between −10 and +10 may be selected using [ ] (and [Shift]).

• The two outputs, P × ε, and Output , are accompanied by bar displays on the right side of the front panel. P × ε simply ranges from −10 V to +10 V. However, since the controller output ranges between the user-programmed upper and lower limits, the output bar display is normalized to that range. For example, if the limits were set to +5 V and −1 V, the full range of the bar display would be 6 V, and 0 V would no longer correspond to the center of the bar display, but would be1/6th of the way up from the bottom. The default limits are ±10 V.

1.2.1 Inputs

• Use [Setpoint] in the INPUTS section of the front panel to choose between an external setpoint input, and the internally generated setpoint. An external setpoint can be supplied at the Setpoint BNC input. When the internal setpoint is selected the BNC connector is disconnected from the SIM960 circuitry.

• The Output BNC connector can be toggled between PID Control mode and Manual mode using [Output] (in the OUTPUT section of the front panel). In manual mode, the SIM960 output is set to the value indicated by the manual parameter.

The common mode range of the “Measure” and “Setpoint” inputs extends from −10V to +10V. If either input is outside this range, the overload LED indicator lights.

The diﬀerential input rangeis ±1 V. Whenever thediﬀerence between Setpoint and Measure exceeds this range, the overload LED indicator turns on. When connected with overall negative feedback and reasonably well tuned, the SIM960 keeps the diﬀerence between the setpoint and measure inputs as small as possible, so the diﬀerential input range is unlikely to be exceeded. Before the SIM960 has been tuned for a given system, however, this may not be true. It is helpful to keep in mind that exceeding the ±1 V diﬀerential input range will saturate the error ampliﬁer, even if theoutput signalwouldotherwise be within the upper and lower Limits setting. In such situations, the controller will be eﬀectively limited at some intermediate value.

SIM960 Analog PID Controller

1.2 Front Panel Operation 1 – 5

1.2.2 Ramping

The ramping feature of the SIM960 PID Controller allows the user to linearly slew the internally generated setpoint level from its current value to a new value. The slew rate may be changed using the SP Ramp parameter on the front panel.

The indicator to the right of SP Ramp shows whether ramping is enabled or disabled. Use [On/Oﬀ] (with SP Ramp selected) to enable/disable ramping. When disabled, changes to the Internal Setpoint parameter take eﬀect immediately. When ramping is enabled, however, changes to Internal Setpoint do not immediately take eﬀect. Instead, Internal (in the Setpoint block of the INPUTS section of the front panel) begins to blink, showing that a new setpoint has been entered and a ramp event is now pending.

To begin the ramp, press [Ramp Start/Stop]. Now, the Internal blink rate doubles, indicating that the setpoint is ramping. To pause the ramp, press [Ramp Start/Stop]˙When the ramp is paused, the In- ternal blink rate becomes uneven. To continue the ramp, press [Ramp Start/Stop] again. When the setpoint reaches the new programmed value, the ramp automatically terminates, and Internal stops blinking.

1.2.3 Connections

Note, SP Ramp has no sign in the numerical display. This is because the polarity of the ramp rate is unambiguously determined by whether the newly entered setpoint is greater or less than the current setpoint. The range of available ramp rates is from 1mV/s to 10,000V/s. For ramp rates less than or equal to 1 V/s, the rate is dynamically trimmed based on real-time measurements from the onboard A-to-D converter.

Connect the sensor output of the system to be controlled to the “Measure”input of the SIM960˙If an external setpoint isto be supplied, connect this to the “Setpoint” input, and use the button in the INPUTS section of the front panel to select “External” input. Before connecting the SIM960 output to the system to control, it may be necessary to set the user programmable output upper and lower Limits to guard against damaging the system. Care should be taken to insure that the programmed output range is consistent with the system input range. Once the limits have been programmed, connect the SIM960 output to the system input.

SIM960 Analog PID Controller

1 – 6 Getting Started

1.2.4 Bar displays

Two LED bar displays have been included on the right side of the SIM960 front panel to provide visual information about the P × ε and Output signals. This reduces the need to frequently return to those ﬁelds on the numerical display while trying to adjust other tuning parameters. Some time should be taken to understand what information these bar displays provide.

Each bar has two lighted LEDs; one for the maximum peak of the signal, and one for the minimum peak. The peaks are determined with respect to time variation of the signal, and they decay back to the DC level with a decay time of ∼100 ms.

To understand how a signal is represented in the bar display, consider an input sine wave of frequency 1 Hz. Since frequency is low compared to the inverse of the decay time, the maximum and minimum peak values are indistinguishable, and the signal appears as a single LED that tracks the sine wave. As the frequency increases, the maximum peak does not decay quickly enough to track the negative excursions the signal, and the minimum peak also fails to track positive excursions. So there appear to be two lighted LEDs slightly separated, roughly tracking the sine wave. As the frequency is further increased to well above the decay time inverse, the two lighted LEDs no longer decay at all from their peak levels, so there appear to be two lighted LEDs marking the maximum and minimum peaks of the sine wave.

Thus, a slowly varying signal appears as a single lighted LED in the display, tracking the signal changes with time. But a quickly varying signal, however, appears as two lighted LEDs marking themaximum and minimum excursions of the signal in time.

The range of the P × ε bar display is ±10 V. The Output bar display has a range determined by the user programmed upper and lower limits. For example, if the limits were set to +5 V and −1 V, the full range of the bar display would be 6 V, and 0 V would no longer correspond to the center of the bar display, but would be1/6th of the way up fromthe bottom. Also, the Output bar display has a red LED on each end to indicate whether the controller output is saturated at its limit.

1.2.5 Restoring the default conﬁguration

The default conﬁguration of the SIM960 can be restored in either of two ways: From the front panel, or via the remote interface.

To restore from the front panel, ﬁrst turn oﬀ the power to the SIM960 by switching its SIM900 Mainframe to “Standby,” then switch the

SIM960 Analog PID Controller

1.3 Rear Panel Monitoring 1 – 7

power on while holding down [Ramp Start/Stop]. Keep the button depressed for about one second after power comes on.

The default conﬁguration can also be restored via the remote interface using the *RST command.

1.3 Rear Panel Monitoring

Two analog monitor signals are available at the rear panel of the SIM960 (see Figure 1.2).

1.3.1 Error Monitor

The upper BNC connector carries a buﬀered copy of the P × ε output of the error ampliﬁer. This output is always available, even when the P term is disabled from the control law. It is also active when the main SIM960 output is set to Manual mode.

1.3.2 Input Setpoint Monitor

The lower BNC is a copy of the internally generated setpoint voltage. This output is also always available, even when the Setpoint mode is set to External.

SIM960 Analog PID Controller

Figure 1.2: The SIM960 rear panel.

1 – 8 Getting Started

1.4 SIM Interface

The primary connection to the SIM960 Analog PID Controller is the rear-panel DB–15 SIM interface connector. Typically, the SIM960 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 SIM960 directly, without using the SIM900 Mainframe. This section provides details on the interface.

CAUTION

The SIM960 has no internal protection against reverse polarity, missing supply, or overvoltage on the power supply pins. Misapplication of power may cause circuit damage. SRS recommends using the SIM960 together with the SIM900 Mainframe for most applications.

1.4.1 SIM interface connector

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

Pin Signal Src ⇒ Dest Description

1 SIGNAL GND MF ⇒SIM Ground reference for signal 2 −STATUS SIM ⇒ MF Status/service request (GND = asserted, +5 V= idle) 3 RTS MF ⇒ SIM HW Handshake (+5V= talk; GND = stop) 4 CTS SIM ⇒MF HW Handshake (+5 V= talk; GND= stop) 5 −REF 10MHZ MF ⇒ SIM 10 MHz reference (optional connection) 6 −5 V MF ⇒ SIM Power supply (no connection in SIM960) 7 −15 V MF ⇒ SIM Power supply (analog circuitry) 8 PS RTN MF ⇒ SIM Power supply return

9 CHASSIS GND Chassis ground 10 TXD MF ⇒ SIM Async data (start bit = “0”= +5V; “1” = GND) 11 RXD SIM ⇒ MF Async data (start bit = “0”= +5 V; “1” = GND) 12 +REF 10MHz MF ⇒ SIM 10MHz reference (optional connection) 13 +5 V MF ⇒ SIM Power supply (digital circuitry) 14

+15 V MF ⇒ SIM Power supply (analog circuitry)

15 +24 V MF ⇒ SIM Power supply (no connection in SIM960)

Direction

1.4.2 Direct interfacing

Table 1.1: SIM Interface Connector Pin Assignments, DB-15

The SIM960 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.

SIM960 Analog PID Controller

1.4 SIM Interface 1 – 9

The mating connector needed is a standard DB–15 receptacle, such as Amp part # 747909-2 (or equivalent). Clean, well-regulated supply voltages of +5,±15VDC must be provided, following the pin-out speciﬁed in Table 1.1. Ground must be provided on Pins 1 and 8, with chassis ground on Pin 9. The −STATUS signal maybemonitored on Pin 2 for a low-going TTL-compatible output indicating a status message.

1.4.2.1 Direct interface cabling

If the user intends to directly wire the SIM960 independent of the SIM900 Mainframe, communication is usually possible by directly connecting the appropriate interface lines from the SIM960 DB–15 plug to the RS-232 serial port of a personal computer.1Connect RXD from the SIM960 directly to RD on the PC, TXD directly to TD, and similarly RTS→RTS and CTS→CTS. In other words, a null-modem style 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 SIM960, 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, makingwhat is sometimes know as a “hydra” cable. The pin-connections are given in Table 1.2.

DB–15/F to SIM960 Name

DB–9/F 3 ←→ 7 RTS 4 ←→ 8 CTS

10 ←→ 3 TxD 11 ←→ 2 RxD

5 Computer Ground

to P/S 7 ←→ −15 VDC

14 ←→ +15 VDC 13 ←→ +5 VDC

8,9 ←→ Ground (P/S return current)

1 ←→ Signal Ground (separate wire to Ground)

Table 1.2: SIM960 Direct Interface Cable Pin Assignments

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

SIM960 Analog PID Controller

1 – 10 Getting Started

1.4.2.2 Serial settings

The initial serial port settings at power-on are: 9600 Baud, 8–bits, no parity, 1 stop bit, and RTS/CTS ﬂow control. These may be changed with the BAUD, FLOW, or PARI commands.

The maximum standard baud rate that the SIM960 supports is 38400. The minimum baud rate is 110. Above 38400, the SIM960 can be set to the following (non-RS–232-standard) baud rates: 62500, 78125, 104167, 156250. Note that these rates are typically not accessible on a standard PC RS–232 port, but can be used between the SIM960 and the SIM900 Mainframe.

SIM960 Analog PID Controller

2 Advanced Topics

In This Chapter

This chapter discusses a simple “closed-loop” tuning procedure, along with some of the advanced features of the SIM960 Analog PID Controller.

2.1 PID Tuning Basics . . . . . . . . . . . . . . . . . . . . 2 – 2

2.2 Ziegler-Nichols’ Tuning . . . . . . . . . . . . . . . . . 2 – 5

2.2.1 Open-loop tuning . . . . . . . . . . . . . . . . . 2 – 5

2.2.2 Closed-loop tuning . . . . . . . . . . . . . . . . 2–6

2.3 Anti-Windup and Conditional Integration . . . . . . 2 – 7

2.4 Bumpless Transfer . . . . . . . . . . . . . . . . . . . . 2 – 8

2.4.1 Manual-to-PID . . . . . . . . . . . . . . . . . . 2 – 8

2.4.2 PID-to-Manual . . . . . . . . . . . . . . . . . . 2 – 8

2 – 1

2 – 2 Advanced Topics

2.1 PID Tuning Basics

PID control provides a simple way to minimize the eﬀect of disturbances to a system. The system consists of a closed feedback loop between two elements, the SIM960 controller and the user pro-

cess. The controller has two inputs, Setpoint and Measure , and an Output. The process consists of a power source that can be directly

changed by the controller, in conjunction witha sensor to monitor the process behavior. The sensor signal, after any necessary conditioning, is the process output. This should be connected to the Measure input of the SIM960, and the SIM960 Output should be connected to the process input, forming a feedback loop.

The diﬀerence between the Setpoint and Measure inputs is the error signal, ε ≡ Setpoint − Measure (Eqn 1.1). In the SIM960 the error signal is ampliﬁed by the proportional gain. The controller uses the ampliﬁed error, P × ε, to generate three control signals:

1. Proportional, the P ampliﬁed error with no changes.

2. Integral, the time integral of the ampliﬁed error signal multiplied by a gain coeﬃcient I.

3. Derivative, the time derivative of the ampliﬁed error signal multiplied by a gain coeﬃcient D.

These signals, as well as an Oﬀset, are combined at a summing junction to produce the controller output (see Eqn 1.2). Figure 2.1 shows a schematic representation of the SIM960 controller topology. Note the proportional gain coeﬃcient is commontoall three terms, so the net integral and derivative gains are P ×I and P ×D, respectively, whether or not proportional control is enabled.

The controller monitors the process output and makes small adjustments to the process in order to minimize deviations of Measure from Setpoint due to external disturbances. To accomplish this, the controller must be properly tuned, meaning that the gains for each of the three control signals—proportional, integral, and derivative— must be chosen appropriately to match the behavior of the process. A well-tuned controller should be able to maintain a stable process output.

The control loop feedback should be negative. However, because the polarity of the process response to the controller output is an arbitrary function of the design of the system, it is vital that the controller polarity be chosen properly. Based on the topology of the SIM960 design, feedback polarity can be changed simplybychanging the polarity of the proportional gain parameter P. The user must ﬁrst determine which polarity will provide negative feedback. If the

SIM960 Analog PID Controller

2.1 PID Tuning Basics 2 – 3

Manual Control

Output

−

× 1

Offset Control

Internal Setpoint/Ramp Generator

SP M

Monitor Output (rear panel BNC)

External Setpoint Input

Measure Input

= SP − M

Output** Selector

* Antiwindup circuitry (see text) ** Bumpless transfer when I is enabled

Output Buffer w/User Controlled Limits

SIM960 Analog PID Controller

Figure 2.1: The SIM960 block diagram.

processisnoninverting, i.e. a small positive change at its input results in a positive change at its output, then using positive P polarity will ensure negative feedback in the loop. Tosee this, follow the eﬀect of a small positive change at the process output. Since the process output is connected to the Measure input of the SIM960, a small positive change would cause a negative change to ε. The resulting change at the controller Outputwould also be negative, as would be that of the process output. Thus, the initial small positive change at the process output is “corrected” by a negative change after going around the feedback loop. As a general rule, if the process is noninverting, then the P-polarity should be positive. If the process is inverting, negative P-polarity should be used.

Care should be taken in designing the process. The sensor should be situated so that it is responsive to changes to the part of the system under control. Placing the sensor too remotely can result in a time delay which limits the quality of control. Also, the sensor should primarily measure the system’s response to external changes, rather than measure the changes directly. The latter can sometimes be used to help the controller anticipate transients, but attheriskof sacriﬁcing accuracy in reaching the target setpoint.

Tuning a PID controller amounts to determining what the relative contributions should be from each of the three types of control. The simplest approach is to start with proportional control and add inte-

2 – 4 Advanced Topics

gral and derivative one at a time. A simple P-controller generates a control variable that is proportional to the error signal.

Increasing the P gain should cause the process output to respond by moving closer to the setpoint. Generally, enough ampliﬁcation should be used so that the process output is broughtreasonably close to the setpoint. Too much gain, however, will cause the system to oscillate. Start with a small P gain, and increase by factors of two until the system begins to oscillate. Then back oﬀ in small amounts until stability is recovered.

While it is possible to maintain stability with a simple P controller, in general this will lead to a ﬁnite, non-zero ε. Increasing P will tend to reduce the resulting ε, but too much proportional gain will eventually lead to oscillations.

One way to eliminate this nonzero error problem is to include an oﬀset at the controller output. The SIM960 Oﬀset parameter can be turned on and adjusted toholdthe process power at a level thatmaintains a smaller error. However, this is only a coarse improvement, since the necessary power level may change with time.

Integral control provides an “automatic” way to dynamically adjust the eﬀective oﬀset to zero the error; in older controllers, integral action was called “automatic reset” for this reason. Integral control simply integrates the error signal with respect to time. Thus the controller output changes until the error has been reduced to zero, near which point the controller output slows and stops changing. If the error drifts over time, the integrator responds by adjusting the controller output to cancel the error. So it is much like having a dynamic output oﬀset constantly responding to system changes. As with proportional gain, too much integral gain can cause oscillation. Again, start with a small I gain and increase by factors of two until oscillation begins, then back oﬀ until stability is recovered.

Though integral control is eﬀective at reducing the error, it is not as eﬀective as proportional control at responding quickly to changes. This is because the integrator needs time to build up a response. To further enhance the response of the process to rapid changes, derivative control is often employed. Derivative control is proportional to the rate of change of the error, so it is relatively unresponsive to slow changes, but rapid changes to the system produce a signiﬁcant response. Derivative control reduces oscillations that can resultfrom step changes to a system.

During the tuning process, it is important to keep in mind that the diﬀerential input range of the SIM960 is ±1.0 V. It is good practice to occasionally glance at the OVLD indicator to ensure the input ampliﬁer is not saturated.

SIM960 Analog PID Controller

2.2 Ziegler-Nichols’ Tuning 2 – 5

2.2 Ziegler-Nichols’ Tuning

For many applications, a good starting point for tuning is one of the two classic Ziegler-Nichols methods2. These two methods are brieﬂy described below; for more details, see, for example, Åstr¨om & H¨agglund, PID Controllers: Theory, Design, and Tuning, Instru- ment Society of America (1995).

2.2.1 Open-loop tuning

The open-loop Ziegler-Nichols method involves introducing a small step change to the process under control, and making a few measurements from the response. The procedure is:

• Switch the SIM960 into Manual mode, and then adjust until the process is stable and near the desired operating point.

• Now make a small, suddenstep change, ∆, in the control signal. Call this time t = 0.

• Record the process response in the Measure signal. Deﬁne the (dimensionless) process step-response function:

h(t) =

Measure(t) −Measure(0)

∆

• Observe the point of maximum slope in h. Extend a straight line through this point, tangent to h, downward(see Figure2.2).

• Let L be the time coordinate where the straight line crosses h = 0; and let a be the negative of the h–intercept (i. e., a > 0 in

Figure 2.2).

• Note thatit is not necessaryto wait for the processto completely settle following the step change ∆—it is suﬃcient to simply wait until the maximum slope is observed in Measure.

From a and L, Ziegler and Nichols suggest tuning for P, PI, and PID control as shown in Table 2.1

Control P I D

P 1/a

PI 0.9/a 1/(3L)

PID 1.2/a 1/(2L) L/2

Table 2.1: Ziegler-Nichols open-loop tuning parameters

SIM960 Analog PID Controller

Ziegler, J. G., & Nichols, N. B. 1942, Trans. ASME, 64, 759

2 – 6 Advanced Topics

h(t)=

Manual(t)

∆

Meas–Meas(0)

maximum slope

2.2.2 Closed-loop tuning

Figure 2.2: The open-loop step response of the process.

An alternate method, also due to Ziegler and Nichols, is based on measuring the gain at which the process just begins to oscillate. The procedure is:

• Switch the SIM960 into PID mode, with I and D both disabled. Choose a value for Setpoint around the desired operating point, and set P so some small value.

• Slowly increase P until the process starts to oscillate.

• Record this value of P as Ku, the “ultimate” gain. Also observe

the period of the oscillations, Tu.

From Kuand Tu, Ziegler and Nichols again suggest tuning for P, PI, and PID control as shown in Table 2.2

Control P I D

P Ku/2

PI 2Ku/5 5/(4Tu)

PID 3Ku/5 2/T

Tu/8

Table 2.2: Ziegler-Nichols closed-loop tuning parameters

SIM960 Analog PID Controller

2.3 Anti-Windup and Conditional Integration 2 – 7

2.3 Anti-Windup and Conditional Integration

For better integral performance, the SIM960 features anti-windup circuitry in the form of conditional integration. The purpose of antiwindup is to improve the controller’s ability to recover from output saturation. When the output saturates, the error is likely to be large, since the process is unable to provide power fast enough to recover the process output. However, the integrator contribution may not account for the full amount of the controller output in this case. Subsequently, the integrator continues to integrate the error until the integrator output saturates. This “winding up” aspect of integral control becomes a problem when the process recovers and the error level passes through zero, because the error must move signiﬁcantly beyond zero for the integrator to “unwind” from saturation. In general, once the controller output is clamped at a limit, nothing is accomplished by drivingit harder into that limit by moreintegration. In fact, it only makes it harder to recover from saturation, since the result is usually large swings back and forth from limit to limit.

There are a variety of anti-windup strategies to mitigate this eﬀect. A simple way to implement anti-windup is to switch oﬀ the integrator whenever the output saturates. This is not the same as resetting the integrator (zeroing its output by discharging the feedback capacitance) because the output simply stops moving, but does not go to zero. It is equivalent to momentarily zeroing the integrator input, so that there is no signal to integrate while the output is saturated.

An improvement to this scheme comes from recognizing that not all saturation conditions cause unwanted integrator wind-up. For example, suppose the controller/process history were such as to produce the following conditions:

• Error signal negative

• Integrator output ﬁnite, not saturated

• Controller output saturated at the positive limit

Then, the integrator output would be moving in the negative direction, since its input, the error, is negative. This would not cause the controller output to be pushed harder into saturation; in fact it may eventually pull it out of saturation. So stopping the integrator would hinder the controller’s eﬀort to recover the process variable. The SIM960 uses a technique called “conditional integration:” Con-

ditional integration only stops the integrator when the polarity of the error is such as to drive the integrator toward the saturated limit.

SIM960 Analog PID Controller

2 – 8 Advanced Topics

2.4 Bumpless Transfer

When switching the output mode between Manual and PID Control, transients on the output signal can disturb the system under control. Minimizing these switching transients is known as “bumpless transfer.” The SIM960 supports bumpless transfer under certain conditions, as described below.

2.4.1 Manual-to-PID

When switching from Manual output to PID Control output, bumpless transfer is only possible if the integral term is enabled.3When I is turned on and the SIM960 is in Manual output mode, the input to the integrator is rerouted to integrate the diﬀerence between Manual and the (deselected) PID Control output. This eﬀectively allows the PID Control to “track” the Manual value, presetting the integrator as necessary. Then, when the output is switched back to PID Control, the controller output is already the same as the Manual output level. Were this not the case, the integrator output would likely saturate while in manual mode, and uponswitching to PID Controlmode, the controller output would suddenly jump. Bumpless transfer insures that the transition from Manual to PID Control mode is smooth.

2.4.2 PID-to-Manual

An additional feature of the SIM960 isthe ability to presetthe manual level to the current PID control output level, so that switching from PID mode to manual mode will also be smooth. With the module in PID mode, select the Manual ﬁeld. Press [On/Oﬀ] and hold it down for at least one second. After one second the manual display reading will shift to the current PID output level. The output mode will remain in PID control mode until it is manually switched on the front panel or through the remote interface. But the new manual output level will be equal to the PID control output.

This can be understood mathematically, since only the integral term has an “unspeciﬁed” initial oﬀset value that can be set to an arbitrary valuewithoutviolating Eqn 1.2.

SIM960 Analog PID Controller

3 Remote Operation

In This Chapter

This chapter describes operating the module over the serial interface.

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

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

3.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 – 7

3.3.1 Power-on conﬁguration . . . . . . . . . . . . . 3 – 7

3.3.2 Buﬀers . . . . . . . . . . . . . . . . . . . . . . . 3 – 7

3.3.3 Device Clear . . . . . . . . . . . . . . . . . . . . 3 – 7

3.4 Commands . . . . . . . . . . . . . . . . . . . . . . . . 3 – 8

3.4.1 Command syntax . . . . . . . . . . . . . . . . . 3 – 8

3.4.2 Examples . . . . . . . . . . . . . . . . . . . . . 3 – 9

3.4.3 Controller settings commands . . . . . . . . . 3 – 10

3.4.4 Controller conﬁguration commands . . . . . . 3 – 12

3.4.5 Monitor commands . . . . . . . . . . . . . . . 3 – 14

3.4.6 Display commands . . . . . . . . . . . . . . . . 3 – 16

3.4.7 Serial communication commands . . . . . . . 3 – 17

3.4.8 Status commands . . . . . . . . . . . . . . . . . 3 – 17

3.4.9 Interface commands . . . . . . . . . . . . . . . 3–20

3.5 Status Model . . . . . . . . . . . . . . . . . . . . . . . 3 – 25

3.5.1 Status Byte (SB) . . . . . . . . . . . . . . . . . . 3 – 26

3.5.2 Service Request Enable (SRE) . . . . . . . . . . 3 – 26

3.5.3 Standard Event Status (ESR) . . . . . . . . . . 3 – 27

3.5.4 Standard Event Status Enable (ESE) . . . . . . 3 – 27

3.5.5 Communication Error Status (CESR) . . . . . . 3 – 27

3.5.6 Communication Error Status Enable (CESE) . 3 – 28

3.5.7 Instrument Status (INCR) . . . . . . . . . . . . 3 – 28

3.5.8 Instrument Status (INSR) . . . . . . . . . . . . 3–29

3.5.9 Analog to Digital Status Enable (INSE) . . . . 3–29

3.5.10 Analog to Digital Status (ADSR) . . . . . . . . 3 – 29

3.5.11 Analog to Digital Status Enable (ADSE) . . . . 3 – 30

3 – 1

3 – 2 Remote Operation

3.1 Index of Common Commands

symbol deﬁnition

i,j Integers f,g Floating-point values 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

Controller Settings

PCTL(?) z 3 – 10 Proportional action ON/OFF ICTL(?) z 3 – 10 Integral action ON/OFF DCTL(?) z 3 – 10 Derivative action ON/OFF OCTL(?) z 3 – 10 Oﬀset ON/OFF GAIN(?) {f } 3 – 10 Proportional Gain APOL(?) z 3 – 11 Controller Polarity INTG(?) {f } 3 – 11 Integral Gain DERV(?) {f } 3 – 11 Derivative Gain OFST(?) {f } 3 – 11 Output Oﬀset

Controller Conﬁguration

AMAN(?) z 3 – 12 Output (Manual Output/PID Control) INPT(?) z 3 – 12 Input (Internal/External Setpoint) SETP(?) {f } 3 – 12 New setpoint RAMP(?) z 3 – 12 Internal setpoint ramping ON/OFF RATE(?) {f } 3 – 12 Setpoint ramping Rate RMPS? 3 – 13 Setpoint ramping status STRT z 3 – 13 Pause or continue ramping MOUT(?) {f } 3 – 13 Manual Output ULIM(?) {f } 3 – 13 Upper Output Limit LLIM(?) {f } 3 – 14 Lower Output Limit

Monitor

SMON? [i] 3 – 14 Setpoint Input Monitor MMON? [i] 3 – 14 Measure Input Monitor EMON? [i] 3 – 15 Ampliﬁed Error Monitor OMON? [i] 3 – 15 Output Monitor RFMT(?) {z} 3 – 15 Output Streaming Records Format SOUT [z] 3 – 16 Stop Streaming FPLC(?) {i} 3 – 16 Frequency of Power Line Cycle

SIM960 Analog PID Controller

3.1 Index of Common Commands 3 – 3

Display

DISP(?) {z} 3 – 16 Select Field SHFT(?) {z} 3 – 16 Shift Status DISX(?) {z} 3 – 17 Front Panel Display Enable

Serial Communications

BAUD(?) {i} 3 – 17 Baud Rate FLOW(?) {z} 3 – 17 Flow Control PARI(?) {z} 3 – 17 Parity

Status

*CLS 3 – 17 Clear Status *STB? [i] 3 – 18 Status Byte *SRE(?) [i,] {j} 3 – 18 Service Request Enable *ESR? [i] 3 – 18 Standard Event Status *ESE(?) [i,] {j} 3 – 18 Standard Event Status Enable CESR? [i] 3 – 18 Comm Error Status CESE(?) [i,]{j} 3 – 19 Comm Error Status Enable INCR? [i] 3 – 19 Instrument condition register INSR? [i] 3 – 19 Instrument status register INSE(?) [i], {j} 3 – 19 Instrument status enable register ADSR? [i] 3 – 19 A-to-D status register ADSE(?) [i], {j} 3 – 19 A-to-D status enable register PSTA(?) {z} 3 – 20 Pulse −STATUS Mode

Interface

*RST 3 – 20 Reset CONS(?) {z} 3 – 21 Console Mode *IDN? 3 – 21 Identify *TST? 3 – 21 Self Test *OPC(?) 3 – 22 Operation Complete WAIT i 3 – 22 Wait LEXE? 3 – 22 Execution Error LCME? 3 – 23 Command Error LBTN? 3 – 23 Last Button TOKN(?) {z} 3 – 24 Token Mode TERM(?) {z} 3 – 24 Response Termination

SIM960 Analog PID Controller

3 – 4 Remote Operation

3.2 Alphabetic List of Commands

*CLS 3 – 17 Clear Status *ESE(?) [i,] {j} 3 – 18 Standard Event Status Enable *ESR? [i] 3 – 18 Standard Event Status *IDN? 3 – 21 Identify *OPC(?) 3 – 22 Operation Complete *RST 3 – 20 Reset *SRE(?) [i,] {j} 3 – 18 Service Request Enable *STB? [i] 3 – 18 Status Byte *TST? 3 – 21 Self Test

ADSE(?) [i], {j} 3 – 19 A-to-D status enable register ADSR? [i] 3 – 19 A-to-D status register AMAN(?) z 3 – 12 Output (Manual Output/PID Control) APOL(?) z 3 – 11 Controller Polarity

BAUD(?) {i} 3 – 17 Baud Rate

CESE(?) [i,]{j} 3 – 19 Comm Error Status Enable CESR? [i] 3 – 18 Comm Error Status CONS(?) {z} 3 – 21 Console Mode

DCTL(?) z 3 – 10 Derivative action ON/OFF DERV(?) {f } 3 – 11 Derivative Gain DISP(?) {z} 3 – 16 Select Field DISX(?) {z} 3 – 17 Front Panel Display Enable

EMON? [i] 3 – 15 Ampliﬁed Error Monitor

FLOW(?) {z} 3 – 17 Flow Control FPLC(?) {i} 3 – 16 Frequency of Power Line Cycle

GAIN(?) {f } 3 – 10 Proportional Gain

SIM960 Analog PID Controller

3.2 Alphabetic List of Commands 3 – 5

ICTL(?) z 3 – 10 Integral action ON/OFF INCR? [i] 3 – 19 Instrument condition register INPT(?) z 3 – 12 Input (Internal/External Setpoint) INSE(?) [i], {j} 3 – 19 Instrument status enable register INSR? [i] 3 – 19 Instrument status register INTG(?) {f } 3 – 11 Integral Gain

LBTN? 3 – 23 Last Button LCME? 3 – 23 Command Error LEXE? 3 – 22 Execution Error LLIM(?) {f } 3 – 14 Lower Output Limit

MMON? [i] 3 – 14 Measure Input Monitor MOUT(?) {f } 3 – 13 Manual Output

OCTL(?) z 3 – 10 Oﬀset ON/OFF OFST(?) {f } 3 – 11 Output Oﬀset OMON? [i] 3 – 15 Output Monitor

PARI(?) {z} 3 – 17 Parity PCTL(?) z 3 – 10 Proportional action ON/OFF PSTA(?) {z} 3 – 20 Pulse −STATUS Mode

RAMP(?) z 3 – 12 Internal setpoint ramping ON/OFF RATE(?) {f } 3 – 12 Setpoint ramping Rate RFMT(?) {z} 3 – 15 Output Streaming Records Format RMPS? 3 – 13 Setpoint ramping status

SETP(?) {f } 3 – 12 New setpoint SHFT(?) {z} 3 – 16 Shift Status SMON? [i] 3 – 14 Setpoint Input Monitor SOUT [z] 3 – 16 Stop Streaming STRT z 3 – 13 Pause or continue ramping

TERM(?) {z} 3 – 24 Response Termination

SIM960 Analog PID Controller

3 – 6 Remote Operation

TOKN(?) {z} 3 – 24 Token Mode

ULIM(?) {f } 3 – 13 Upper Output Limit

WAIT i 3 – 22 Wait

SIM960 Analog PID Controller

3.3 Introduction 3 – 7

3.3 Introduction

Remote operation of the SIM960 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 SIMmainframe or directly via RS-232 (see section 1.4.2.1).

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

3.3.1 Power-on conﬁguration

The settings for the remote interface are 9600 baud with no parity and hardware ﬂow control, and local echo disabled (CONS OFF).

Most of the SIM960 instrument settings are stored in non-volatile memory, and at power-on the instrument returns to the state it was last in when power was removed. Exceptions are noted in the command descriptions.

Reset values of parameters are shown in boldface.

3.3.2 Buffers

3.3.3 Device Clear

The SIM960 stores incoming bytes from the host interface in a 32byte 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 SIM960 are buﬀered in a 32-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 SIM960 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 interface is reset to 9600 baud and CONS mode is turned OFF. Note that this only resets the communi- cation interface; the basic function of the SIM960 is left unchanged; to reset the meter, see *RST.

The Device Clear signal will also terminate any streaming outputs fromtheSIM960duetoanSMON?, MMON?, EMON? and/or OMON? query of multiple conversions.

SIM960 Analog PID Controller

3 – 8 Remote Operation

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 sequence 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 any 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 whitespace are ignored. Execution of the command does not begin until the command terminator is received.

Token parameters (generically shown as z in the command de-tokens scriptions) can be speciﬁed either as a keyword or 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.

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

SIM960 Analog PID Controller

3.4 Commands 3 – 9

symbol deﬁnition

i,j Integers f,g Floating-point values 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

3.4.2 Examples

Each command is provided with a simple example illustrating its usage. In these examples, all data sent by the host computer to the SIM960 are set as straight teletype font, while responses received the host computer from the SIM960 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, but are intended to provide a convenient starting point for user programming.

SIM960 Analog PID Controller

3 – 10 Remote Operation

3.4.3 Controller settings commands

Proportional action ON/OFFPCTL(?) z Set (query) the proportional control {to z=(OFF 0, ON 1)}.

When ON, the PID Control path includes the proportional control term.

PCTL 1Example:

Integral action ON/OFFICTL(?) z Set (query) the integral control {to z=(OFF 0, ON 1)}.

When ON, the PID Control path includes the integral control term.

ICTL?Example:

Derivative action ON/OFFDCTL(?) z Set (query) the derivative control {to z=(OFF 0, ON 1)}.

When ON, the PID Control path includes the derivative control term.

DCTL OFFExample:

Oﬀset ON/OFFOCTL(?) z Set (query) the oﬀset control {to z=(OFF 0, ON 1)}.

When ON, the PID Control path includes the constant output oﬀset.

OCTL?Example:

Proportional GainGAIN(?) {f } Set (query) the proportional gain (P) {to f }, in V/V.

Values may be entered in decimal or exponential format, and are signed.

GAIN may be set with 2 digits of resolution for 1.0 ≤ |P| ≤ 103, and with single-digit resolution for 0.1 ≤ |P| ≤ 0.9. Note that setting GAIN does not modify whether the proportional term is enabled or disabled. For on/oﬀ control, see PCTL.

Setting GAIN overrides the previous setting of APOL. The allowed range for GAIN is 10−1≤ |P| ≤ 103.

GAIN +2.5E+2Example:

SIM960 Analog PID Controller

3.4 Commands 3 – 11

Controller PolarityAPOL(?) z Set (query) the proportional gain polarity {to z=(POS 1, NEG 0)}. Set-

ting APOL will override the sign of a previously-commanded GAIN.

APOL?Example:

POS

Integral GainINTG(?) {f } Set (query) the integral gain (I) {to f }, in V/(V·s).

INTG may be set with 2 digits of resolution for 10−1≤ I ≤ 5 × 105, and with single-digit resolution for 10−2≤ I ≤ 9 × 10−2. Integral gains are unsigned (positive values only). Note that setting INTG does not modify whether the integrator is enabled or disabled. For on/oﬀ control, see ICTL.

The allowed range for INTG is 10−2≤ I ≤ 5 × 105.

INTG?Example:

+1.5E+3

Derivative GainDERV(?) {f } Set (query) the derivative gain {to f }, in V/(V/s).

DERV may be set with 2 digits of resolution for 10−5≤ D ≤ 10, and with single-digit resolution for 10−6≤ I ≤ 9 × 10−6. Derivative gains are unsigned (positive values only). Note that setting DERV does not modify whether the derivative is enabled or disabled. For on/oﬀ control, see DCTL.

The allowed range for DERV is 10−6≤ D ≤ 10.

DERV 0.000015Example: DERV?

+1.5E-5

Output OﬀsetOFST(?) {f } Set (query) the output oﬀset {to f }, in volts.

The oﬀset voltage can be set with millivolt resolution. Note that setting OFST does not modify whether the oﬀset is enabled or disabled. For on/oﬀ control, see OCTL.

The allowed range is −10.000 ≤ OFST +10.000.

OFST -12.3E-2; OFST?Example:

-0.123

SIM960 Analog PID Controller

3 – 12 Remote Operation

3.4.4 Controller conﬁguration commands

Output (Manual Output/PID Control)AMAN(?) z Set (query) controller output state {to z=(MAN 0, PID 1)}.

AMAN?Example:

Input (Internal/External Setpoint)INPT(?) z Set (query) setpoint input state {to z=(INT 0, EXT 1)}.

INPT INTExample:

New setpointSETP(?) {f } Set (query) the setpoint value {to f }, in volts.

The setpoint can be set with millivolt resolution. If ramping is enabled (see RAMP), SETP will initiate a ramp to f. Otherwise, the setpoint value changes immediately to the new value.

The allowed range is −10.000 ≤ SETP ≤ +10.000.

SETP -1.234Example:

Internal setpoint ramping ON/OFFRAMP(?) z Set (query) internal setpoint ramping {to z=(OFF 0, ON 1)}.

When ON, the changes to the internal setpoint are made with constant slew-rate ramping enabled.

RAMP 1Example:

Setpoint ramping RateRATE(?) {f } Set (query) the setpoint rate {to f }, in V/s.

RATE may be set with 2 digits of resolution for values above 10−2, and with signle-digit resolution below that. Note that setting RATE does not modify whether setpoint changes are made with constant slew-rate ramping or not. For on/oﬀ control of linear ramping, see RAMP.

The allowed range is 10−3≤ RATE ≤ 104.

RATE 2.2E-3Example: RATE?

+0.2E-2

SIM960 Analog PID Controller

3.4 Commands 3 – 13

Setpoint ramping statusRMPS? Query the ramp status.

For slow ramps of the internal setpoint, the RMPS? query will monitor the real-time status of a setpoint transition.

The response is one of the following token values: IDLE 0, PENDING

1, RAMPING 2, PAUSED 3.

RMPS?Example:

RAMPING

Pause or continue rampingSTRT z Cause a setpoint ramping event in progress to pause (STOP) or con-

tinue (START). z=(STOP 0, START 1). Note that STRT cannot be used to initiate a new setpoint transition

from the RMPS PENDING state—this can only be accomplished by pressing [Ramp Start/Stop] on the front panel.

STRT STARTExample:

Manual OutputMOUT(?) {f } Set (query) the manual output value {to f }, in volts.

The manual output can be set with millivolt resolution. Note that setting MOUT does not modify whether the controller is in manual or PID control mode. For on/oﬀ control of manual output, see AMAN.

The allowed range for MOUT is −10.000 ≤ MOUT ≤ +10.000.

MOUT?Example:

+8.000

Upper Output LimitULIM(?) {f } Set (query) the upper output limit {to f }, in volts.

The upper limit can be set with 10mV resolution. Note that, regardless of the operating mode of the SIM960 (see AMAN), the output voltage will always be clamped to remain less positive than the ULIM limit. Combined with the LLIM limit, this results in the output obeying:

The allowed range is LLIM ≤ ULIM ≤ +10.00.

SIM960 Analog PID Controller

−10.00 ≤ LLIM ≤ Output ≤ ULIM ≤ +10.00

3 – 14 Remote Operation

Lower Output LimitLLIM(?) {f} Set (query) the lower output limit {to f }, in volts.

The lower limit can be set with 10 mV resolution. The output voltage of the SIM960 will always be clamped to remain less negative than the LLIM limit. See ULIM for more details.

The allowed range is −10.00 ≤ LLIM ≤ ULIM.

3.4.5 Monitor commands

Setpoint Input MonitorSMON? [i] Query the Setpoint input voltage to the error ampliﬁer, in volts.

If INPT INT is set, then SMON? monitors the value of the internallygenerated setpoint. If INPT EXT, then SMON? monitors the voltage applied at the front-panel Setpoint BNC input.

i is an optional parameter that causes streaming of Setpoint data. If i is speciﬁed, then i measurements will be output at a rate of approximately two measurements per second. If i is speciﬁed as 0, then measurements will be output indeﬁnitely. The SOUT command can be used to stop streaming.

SETP 1.2; SMON? 5Example:

+01.004496 +01.066567 +01.128909 +01.191273 +01.200073

Measure Input MonitorMMON? [i] Query the Measure input voltage to the error ampliﬁer, in volts.

MMON? always reports the voltage applied at the front-panel Measure BNC input.

i is an optional parameter that causes streaming of Measure data. If i is speciﬁed, then i measurements will be output at a rate of approximately half a second per measurement. If i is speciﬁed as 0, then measurements will be output indeﬁnitely. The SOUT command can be used to stop streaming.

MMON?Example:

-00.005900

SIM960 Analog PID Controller

3.4 Commands 3 – 15

Ampliﬁed Error MonitorEMON? [i] Query the P × ε voltage, in volts.

i is an optional parameter that causes streaming of (P × ε) data. If i is speciﬁed, then i measurements will be output at a rate of approximately half a second per measurement. If i is speciﬁed as 0, then measurements will be output indeﬁnitely. The SOUT command can be used to stop streaming.

EMON?Example:

+00.105537

Output MonitorOMON? [i] Query the Output voltage, in volts.

OMON? alwaysreportsthevoltagegeneratedatthefront-panelOUTPUT BNC connector (regardless of the state of AMAN).

i is an optional parameter that causes streaming of Output data. If i is speciﬁed, then i measurements will be output at a rate of approximately half a second per measurement. If i is speciﬁed as 0, then measurements will be output indeﬁnitely. The SOUT command can be used to stop streaming.

OMON?Example:

+01.106139

Output Streaming Records FormatRFMT(?) {z} Set (query) the output streaming record format {to z=(OFF 0, ON 1)}.

When ON, data are output on a single line with three comma delimiters. Since there are four monitor channels that can be streamed to output, and any combination of the four may be streamed, thecomma delimiters allow unambiguous identiﬁcation of channel data.

The record format is hSMONi,hMMONi,hEMONi,hOMONi

RFMT ONExample: SMON? 3; MMON? 3; EMON? 3; OMON? 3

+00.099909,-00.006053,+00.105601,+01.106135 +00.099909,-00.006031,+00.105615,+01.106123 +00.099915,-00.006001,+00.105636,+01.106151

SIM960 Analog PID Controller

3 – 16 Remote Operation

Stop StreamingSOUT [z] Turn oﬀ streaming (of channel z= (SMN 0, MMN 1, EMN 2, OMN 3)).

If the optional parameter z is not speciﬁed, then all streaming outputs are turned oﬀ.

SOUTExample:

Frequency of Power Line CycleFPLC(?) {i} Set (query) the power line cycle frequency {to i=(50, 60)} Hz.

FPLC is used to program the power-line rejection frequency for the precision voltage monitors (SMON?, MMON?, EMON?, OMON?).

FPLC?Example:

3.4.6 Display commands

Select FieldDISP(?) {z} Set (query) the ﬁeld level to be displayed {to z}. Allowed values of z

are

PRP 0 Proportional gain

IGL 1 Integral gain DER 2 Derivative gain OFS 3 Output oﬀset RTE 4 Setpoint rate STP 5 Setpoint value MNL 6 Manual output value ULM 7 Upper limit of output LLM 8 Lower limit of output SMN 9 ADC measurement of Setpoint input MMN 10 ADC measurement of Measure input EMN 11 ADC measurement of P-Ampliﬁed error OMN 12 ADC measurement of PID/Manual Output

DISP 1Example:

Shift StatusSHFT(?) {z} Set (query) the current shift status {to i=(OFF 0, ON 1)}.

SHFT?Example:

OFF

SIM960 Analog PID Controller

3.4 Commands 3 – 17

Front Panel Display EnableDISX(?) {z} Set (query) the front panel display status {to z=(OFF 0, ON 1)}.

When the display is turned oﬀ (DISX OFF), all front panel indicators and buttons are disabled.

DISX OFFExample:

3.4.7 Serial communication commands

Baud RateBAUD(?) {i} Set (query) the baud rate {to i}.

At power-on, the baud rate defaults to 9600. Changing baud rate must be carefully orchestrated to ensure proper connectivity throughout the transaction (see the SIM900 manual discussion of the BAUD command for more examples).

BAUD 38800Example:

3.4.8 Status commands

Flow ControlFLOW(?) {z} Set (query) ﬂow control {to z=(NONE 0, RTS 1, XON 2)}.

At power-on, the SIM960 defaults to FLOW RTS ﬂow control.

FLOW 0Example:

ParityPARI(?) {z} Set (query) parity {to z = (NONE 0, ODD 1, EVEN 2, MARK 3, SPACE 4)}.

At power-on, the SIM960 defaults to PARI NONE.

PARI?Example:

NONE

The Status commands query and conﬁgure registers associated with status reporting of the SIM960.

Clear Status*CLS *CLS immediately clears the ESR, CESR, and the SIM960 status reg-

isters.

*CLSExample:

SIM960 Analog PID Controller

3 – 18 Remote Operation

Status Byte*STB? [i] Reads 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 32; *SRE? 5Example:

Standard Event Status*ESR? [i] Reads the Standard Event Status Register [bit i].

Upon executing *ESR?, the returned bit(s) of the ESR register are cleared.

GAIN 0Example: ESR?

The binary value (16) corresponds to anExecutionError, since GAIN 0 is an illegal value (minimum gain is 0.1).

Standard Event Status Enable*ESE(?) [i,] {j} Set (query) the Standard Event Status Enable Register [bit i] {to j}.

*ESE 16Example:

Comm Error StatusCESR? [i] Query Comm Error Status Register [for bit i].

Upon executing a CESR? query, the returned bit(s) of the CESR register are cleared.

CESR?Example:

SIM960 Analog PID Controller

3.4 Commands 3 – 19

Comm Error Status EnableCESE(?) [i,]{j} Set (query) Comm Error Status Enable Register [bit i] {to j}.

CESR 0Example:

Instrument condition registerINCR? [i] Query the instrument condition register [bit i].

The values of the bits in the instrument condition register are determined by the current (real-time) condition of the events deﬁned in the instrument status register (see Section 3.5.8).

Reading the instrument condition register does not aﬀect the register.

INCR?Example:

Instrument status registerINSR? [i] Query the instrument status register [bit i].

INSR?Example:

Instrument status enable registerINSE(?) [i], {j} Set (query) the instrument status enable register [bit i] {to j}.

INSE 16Example:

A-to-D status registerADSR? [i] Query the analog to digital status register [bit i].

When new data become available from the A-to-D converter, the Ato-D status register bit corresponding to the channel of the new data is set (see Section 3.5.10).

ADSR?Example:

A-to-D status enable registerADSE(?) [i], {j} Set (query) the A-toD status enable register [bit i] {to j}.

ADSE 2Example:

SIM960 Analog PID Controller

3 – 20 Remote Operation

Pulse −STATUS ModePSTA(?) {z} Set (query) the Pulse −STATUS Mode {to z=(OFF 0, ON 1)}.

When PSTA ON is set, any new service request 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.

At power-on, PSTA is set to OFF.

PSTA?Example:

OFF

3.4.9 Interface commands

The Interface commands provide control over the interface between the SIM960 and the host computer.

Reset*RST Reset the SIM960 to its default conﬁguration. The eﬀect of this com-

mand is equivalent to the following sequence of commands:

• DISX ON

• DISP PRP

• SHFT OFF

• GAIN 1.0

• APOL POS

• INTG 1.0

• DERV 1.0E-6

• OFST 0.0

• RATE 1.0

• PCTL ON

• ICTL OFF

• DCTL OFF

• OCTL OFF

• RAMP OFF

• SETP 0.0 (must not precede RAMP OFF)

• MOUT 0.0

• ULIM +10.0

SIM960 Analog PID Controller

3.4 Commands 3 – 21

• LLIM -10.0

• INPT EXT

• AMAN PID

• TOKN OFF

• SOUT

The baud rate of the SIM960 is unaﬀected by *RST. The entire status model is also unaﬀected by *RST.

*RSTExample:

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

CONS causes each character received at the Input Buﬀer to be copied to the Output Queue.

At power-on, CONS is set to OFF.

CONS ONExample:

Identify*IDN? Read the device identiﬁcation string.

The identiﬁcation string is formatted as:

Stanford Research Systems,SIM960,s/n******,ver#.#

where SIM960 is the model number, ****** is the 6-digit serial number, and #.# is the ﬁrmware revision level.

*IDN?Example:

Stanford Research Systems,SIM960,s/n003173,ver2.15

Self Test*TST? There is no internal self-test in the SIM960, so this query always

returns 0.

*TST?Example:

SIM960 Analog PID Controller

3 – 22 Remote Operation

Operation Complete*OPC(?) Operation Complete. Sets the OPC ﬂag in the ESR register.

The query form *OPC? writes a 1 in the Output Queue when complete, but does not aﬀect the ESR register.

*OPC?Example:

WaitWAIT i Wait i milliseconds before processing morecommands from the host.

When using the WAIT command, be careful to not overﬂow the input buﬀer of the SIM960 (see section 3.3.2).

SETP 0Example: RATE 0.1 SETP 1.0; WAIT 5000; SMON?

+00.483159

Execution ErrorLEXE? Query the last execution error code. Valid codes are:

Value Deﬁnition

0 No execution error since last LEXE? 1 Illegal value 2 Wrong token 3 Invalid bit

16 Invalid parameter 17 Missing parameter 18 No change 20 Ramp in progress 21 Limits conﬂict

*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.

SIM960 Analog PID Controller

3.4 Commands 3 – 23

Command ErrorLCME? Query the last command error code. Valid codes are:

Value Deﬁnition

0 No execution 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 13 Bad hex block 14 Unknown token

*IDNExample: LCME?

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

Last ButtonLBTN? Query the last button that was pressed. The values returned are:

Value Button

0 no button pressed since last LBTN? 1 [Setpoint] 2 [Output] 3 [Ramp Start/Stop] 4 [Shift] 5 [Select] 6 [On/Oﬀ] 7 [ ]/ [ ] 8 [ ]/ [ ]

LBTN?Example:

SIM960 Analog PID Controller

3 – 24 Remote Operation

Token ModeTOKN(?) {z} Set (query) the Token Query mode {to z=(OFF 0, ON 1)}.

If TOKN ON is set, then queries to the SIM960 that return tokens will return the text keyword; otherwise they return the decimal integer value.

Thus, the only possible responses to the TOKN? query are ON and 0. At power-on, TOKN is set to OFF.

TOKN OFFExample:

Response TerminationTERM(?) {z} Set (query) the htermi sequence {to z=(NONE 0, CR 1, LF 2, CRLF 3,

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.

At power-on, the default is TERM CRLF.

TERM?Example:

SIM960 Analog PID Controller

3.5 Status Model 3 – 25

CESB

MSS

ESB

IDLE

undef

ADSB

INSB

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 Overrun

OVR: Input Buffer Overrun

RTSH: RTS Halted

CTSH: CTS Halted

DCAS: Device Clear

NOISE: Noise Error

CESR CESE

Communication Error Status

STATUS

ADSETP: Setpoint Mon

ADMEAS: Measure Mon

ADOUT: Output Mon

undef

ADERR: Error Signal Mon

ADSR ADSE

Analog to Digital Status

OVLD

ULIMIT

ANTIWIND

RSTOP

undef

LLIMIT

Instrument Status

INSEINSR

INCR

3.5 Status Model

The SIM960 status registers follow the hierarchical IEEE–488.2 format. AblockdiagramofthestatusregisterarrayisgiveninFigure3.1.

Condition Registers : These read-only registers correspond to the real-time condi-

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

SIM960 Analog PID Controller

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

Figure 3.1: Status Register Model for the SIM960 Analog PID Controller.

There are three categories of registers in the SIM960 status model:

tion of some underlying physical property being monitored. Queries return the latest value of the property, and have no other eﬀect. Condition register names end with CR.

events. If the event occurs, the corresponding bit is set to

1. Upon querying an event register, any set bits within it are cleared These are sometimes known as “sticky bits,” since once set, a bit can only be clearedby reading its value. Event register names end with SR.

responding event register. If any 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 – 26 Remote Operation

3.5.1 Status Byte (SB)

The Status Byte is the top-level summary of the SIM960 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 INSB 2 1 ADSB 4 2 undef (0)

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

128 7 CESB

INSB : Instrument Status SummaryBit. Indicates whether one or more

of the enabled ﬂags in the Instrument Status Register has become true.

ADSB : Analog to Digital Status Bit. Indicates whether one or more of

the enabled ﬂags in the Analog to Digital 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 SIM960 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/RQS. 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.

This register is cleared at power-on.

SIM960 Analog PID Controller

3.5 Status Model 3 – 27

3.5.3 Standard Event Status (ESR)

The Standard Event Status register consists of 8 event ﬂags. These event ﬂags areall “sticky bits” that are set by the corresponding event, and cleared only by reading or with the *CLS command. Reading a single bit (with the *ESR? i query) clears only bit i.

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. Undeﬁned for SIM960.

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

successfully parsed. Out-of-range parameters are an example. The error code can be queried with LEXE?.

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

code can be queried with LCME?.

URQ : User Request. Indicates 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). It can be set and queried with the *ESE(?) command.

This register is cleared at power-on.

3.5.5 Communication Error Status (CESR)

The Communication Error Status register consists of 8 event ﬂags; each of which is set by the corresponding event, and cleared only by reading or with the *CLS command. Reading a single bit (with the CESR? i query) clears only bit i.

SIM960 Analog PID Controller

3 – 28 Remote Operation

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

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

byte.

FRAME : Framing Error. Set when an incoming serialdata byteis 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 incoming data. Causes the Input Buﬀer to be ﬂushed, and resets the command parser.

RTSH : Undeﬁned for the SIM960. Command Error. Indicates a parser-

detected error.

CTSH : Undeﬁned for the SIM960.

DCAS : Device Clear. Indicates the SIM960 received the Device Clear

signal (an RS-232 hbreaki). Clears the Input Buﬀer and 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). It can be set and queried with the CESE(?) command.

This register is cleared at power-on.

3.5.7 Instrument Status (INCR)

The Instrument Condition Register consists of 5 single-bit monitors of condition events within the SIM960. Bits in the INCR reﬂect the real-time values of their corresponding signals. Reading the entire register, or individualbits within it, does not aﬀect thevalue of INCR.

SIM960 Analog PID Controller

3.5 Status Model 3 – 29

Weight Bit Flag

1 0 OVLD

2 1 ULIMIT

4 2 LLIMIT

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

128 7 undef (0)

OVLD : Ampliﬁer Overload. Set to indicate an overload (either diﬀer-

ential or common-mode) is presently occurring in the front-end ampliﬁer.

ULIMIT : Upper Limit Reached. Set to indicate the output signal is

presently saturated into the programmable upper-limit voltage.

LLIMIT : Lower Limit Reached. Set to indicate the output signal is

presently saturated into the programmable lower-limit voltage.

ANTIWIND : Anti-windup Active. Set to indicate the anti-windup circuit is

actively inhibiting integration of the error signal.

RSTOP : Ramp Stopped. Set to indicate that no internal setpoint ramp is

in progress; cleared to indicate ramping is presently underway.

3.5.8 Instrument Status (INSR)

The Instrument Status Register consists of (latching) event ﬂags that correspond one-to-one with the bits of the INCR (see above). Upon the transition 0 → 1 of any bit within the INCR, the corresponding bit in the INSR becomes set.

Bits in the INSR are unaﬀected by the 1 → 0 transitions in the INCR, and are cleared onlyby reading or with the *CLS command. Reading a single bit (with the INSR? i query) clears only bit i.

3.5.9 Analog to Digital Status Enable (INSE)

The INSE acts as a bitwise AND with the INSR register to produce the single bit INSB message in the Status Byte Register (SB). It can be set and queried with the INSE(?) command.

This register is cleared at power-on.

3.5.10 Analog to Digital Status (ADSR)

The Analog to Digital Status Register consists of 4 event ﬂags; each of which is set by a corresponding conversion completion for one of

SIM960 Analog PID Controller

3 – 30 Remote Operation

the 4 monitored analog signals. Bits in the ADSR are cleared only by reading or with the *CLS command. Reading a single bit (with the ADSR? i query) clears only bit i.

Weight Bit Flag

1 0 ADSETP

2 1 ADMEAS

4 2 ADERR

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

128 7 undef (0)

ADSETP : Setpoint Monitor Conversion Complete. Indicates a new con-

version result is available for SMON?.

ADMEAS : Measure Monitor Conversion Complete. Indicates a new con-

version result is available for MMON?.

ADERR : Ampliﬁed Error Monitor Conversion Complete. Indicates a

new conversion result is available for EMON?.

ADOUT : Output Monitor Conversion Complete. Indicates a new con-

version result is available for OMON?.

While reading this register (with the ADSR? query) will clear any Tripn bit(s) that are set, it will not reset the overvoltage protection circuit. To do that, the user must issue the TRIP command. As long as a channel remains tripped oﬀ, the Tripn bit will continuously be reasserted.

3.5.11 Analog to Digital Status Enable (ADSE)

The ADSE acts as a bitwise AND with the ADSR register to produce the single bit ADSB message in the Status Byte Register (SB). It can be set and queried with the ADSE(?) command.

This register is cleared at power-on.

SIM960 Analog PID Controller

4 Performance Tests

In This Chapter

This chapter describes the tests necessary to verify the SIM960 is operating correctly and within speciﬁed calibration.

4.1 Getting Ready . . . . . . . . . . . . . . . . . . . . . . . 4 – 2

4.2 Performance Tests . . . . . . . . . . . . . . . . . . . . 4 – 2

4.2.1 Input Ampliﬁer Oﬀset . . . . . . . . . . . . . . 4 – 2

4.2.2 A to D Converter test . . . . . . . . . . . . . . . 4–2

4.2.3 Proportional Gain Accuracy . . . . . . . . . . . 4 – 3

4.2.4 Derivative Gain Accuracy . . . . . . . . . . . . 4–4

4.2.5 Integral Gain Accuracy . . . . . . . . . . . . . 4 – 5

4.2.6 Ramp Rate Accuracy . . . . . . . . . . . . . . . 4 – 5

4.2.7 Oﬀset Control Accuracy . . . . . . . . . . . . . 4 – 6

4.2.8 Manual Output Accuracy . . . . . . . . . . . . 4 – 6

4.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . 4 – 6

4 – 1

4 – 2 Performance Tests

4.1 Getting Ready

Recommended instruments include:

1. SRS SIM900 Mainframe

2. Agilent 3458A 81/2 digit multimeter

3. SRS SR620 Time interval counter

4. SRS SR785 Dynamic signal analyzer

5. PC with remote interface to SIM900 Mainframe

Also needed is a 96:1 resistive divider formed by soldering two resistors, a 210.0 Ω and a 20.00 kΩ resistor (both ±0.1%) in series. The resulting three conductors of this network will be labeled for future reference as follows: The conductor running between the resistors will be called the “center”, the conductor on the 210 Ω end will be the “bottom”, and the conductor on the 20 kΩ end will be the “top”. This divider will be used externally to the SIM960 to test the integral gain accuracy.

The SIM960 should begiven at least onehour to warm upafter power is turned on, and careshould be taken not to constrict the ventillation holes in the SIM900 mainframe. It should be located in a room with stable temperature, preferably from 65 to 75 degrees F.

4.2 Performance Tests

4.2.1 Input Ampliﬁer Offset

4.2.2 A to D Converter test

The various subsystems of the SIM960 can be tested with the following procedures. In all cases, if the measurement is outside the tolerance or range indicated, then the SIM960 is out of calibration.

Ground the two inputs, ’Setpoint’ and ’Measure’ of the SIM960 using BNC grounding caps or 50 Ω terminators. Using the remoteinterface, reset the SIM960 using the *RST command. Select ’External’ by pressing [Setpoint] on the front panel. Adjust the P (gain) parameter to 1000 (maximum gain). Use the Multimeter to measure the Error output at the rear panel BNC of the SIM960. Switch the polariy of the P (gain) parameter and observe the change at the rear panel Error BNC. The readings for both polarities should be within ±10 mV of zero.

• Reset the SIM960 using the *RST command.

SIM960 Analog PID Controller

4.2 Performance Tests 4 – 3

• Set the P (gain) parameter to +8 using GAIN 8.0.

• Turn oﬀ P control using PCTL OFF.

• Set the I parameter to 105using INTG 1.0E5.

• Turn on I control using ICTL ON.

• Use a short BNC cable to connect the SIM960 Output to the

Measure input.

• Select “Internal” by pressing [Setpoint] on the front panel.

• Select “Setpoint” and observe the displayed value. It should be within ±10 mV of 0.000 V.

• Select “Measure”. It should also be within ±10 mV of 0.000 V.

• Select “Output”. It should also be within ±10 mV of 0.000 V.

• Set the internal setpoint to +8.000 V by sending SETP +8.0,

and repeat the previous three steps, each time observing that the displayed value is within ±10 mV of +8.000 V.

• Set the internal setpoint to −8.000V by sending SETP -8.0, and repeating the same three measurements, each time observing that the displayed value is within ±10 mV of −8.000 V.

• Now disconnect the Output from the Measure input, and ground the Measure input using a BNC grounding cap or 50 Ohm terminator.

• Turn oﬀ I control using ICTL OFF, and turn on P control using PCTL ON. The P (gain) parameter should still be 8.0.

• Change theinternalsetpoint to 0.000 V using SETP 0, and select the P × ε display level. The value displayed should be within

±50 mV of 0.000 V.

• Now change the internal setpoint to +1.000 V using SETP +1. The P × ε value should be within ±50 mV of +8.000 V.

• Change the internal setpoint to −1.000 V using SETP -1. The P × ε value should be within ±50 mV of -8.000 V.

4.2.3 Proportional Gain Accuracy

Reset the SIM960 via the remote interface using *RST. Ground the Measure input. Connect the Source output of the SR785 to the SR785 Channel 1A input, and to the SIM960 Setpoint input. Connect the SIM960 ouput to the SR785 Channel 2A input. With the SR785 in swept sine mode measure the frequency response at 1 kHz, adjusting

SIM960 Analog PID Controller

4 – 4 Performance Tests

the source output amplitude for each P (gain) setting from the table below.

P(gain) Source amplitude (volts) 8 0.5

8.1 0.5 16 0.3

16.1 0.3 32 0.15 33 0.15 64 0.08 65 0.08 128 0.04 129 0.04 250 0.02 260 0.02 510 0.01 520 0.01 1000 0.005

In each case the frequency response should be within ±1% of the programmed gain value. The gain should not vary by more than ±1% over the full 100 kHz bandwidth at the P (gain) = 8 setting.

4.2.4 Derivative Gain Accuracy

Use the same connections as for the proportional gain accuracy test. Reset the SIM960 via the remote interface using *RST. Turn oﬀ the P (gain) control using PCTL OFF. Turn on the D control using DCTL ON. With the SR785 in swept sine mode and the source output amplitude at 0.5 V, measure the frequency response atthe frequencies below for each D setting.

In each case the frequency response should be within ±2% of the programmed gain value.

D (sec) frequency expected response

1.00 × 10

1.01 × 10

1.00 × 10

1.01 × 10

1.00 × 10

1.01 × 10

1.00 × 10

1.01 × 10

1.00 × 10

1.01 × 10

−5

1.600 kHz 0.10053

−5

1.600 kHz 0.10154

−4

1.600 kHz 1.0053

−4

1.600 kHz 1.0154

−3

160 Hz 1.0053

−3

160 Hz 1.0154

−2

−1

16 Hz 1.0053 16 Hz 1.0154

1.6 Hz 1.0053

1.6 Hz 1.0154

SIM960 Analog PID Controller

4.2 Performance Tests 4 – 5

4.2.5 Integral Gain Accuracy

Use the same connections as for the proportional and derivative gain accuracy tests, but now add the divider network to form a closedloop conﬁguration.

• Connect the top of the divider to the Output of the SIM960, connect the center of the divider to the Measure input of the SIM960, and connect the bottom of the divider to ground. This ground should be accessed at one of the BNC shields.

• Reset the SIM960 via the remote interface using *RST.

• Set the P (gain) parameter to 8.0 using GAIN 8.0.

• Turn oﬀ the P (gain) control using PCTL OFF.

• Turn on the I control using ICTL ON.

• With the SR785 in swept sine mode and the source output

amplitude at 0.5 V, measure the frequency response at the frequencies below for each I setting.

4.2.6 Ramp Rate Accuracy

I (1/sec) frequency expected response

5 10 Hz 0.6366

100 150 Hz 0.8488 2×1033.0 kHz 0.8488 5×104100 kHz 0.6366 5×105100 kHz 6.366

In each case the frequency response should be within ±2% of the programmed gain value.

To test the ramp rate, wire the SIM960 as a ’follower’ by connecting the output to the Measure input. Reset the SIM960 using *RST. Set the P (gain) to 8.0 using GAIN 8.0, and turn oﬀ the P control using PCTL OFF. Turn on I control using ICTL ON, and set the I parameter to 105using INTG 1.0E5.

The Setpoint input should be set to Internal using INPT INT, and ramping should be enabled using RAMP ON. The Multimeter can be used to measure the SIM960 output during a ramp. Set up the multimeter to take 10-20 samples at a known time interval during a ramp, based on the ramp rate being tested, and the range of the ramp. Then extract the ramp rate by calculating the average slope of the ramp data using a least squares ﬁt routine. For each ramp rate being tested, measure both a positive going ramp and a negative one, and calculate the average ramp rate magnitude.

SIM960 Analog PID Controller

4 – 6 Performance Tests

Rate (V/sec)

0.01

0.1

0.101

2.0

2.1 35 36 600 610 10000

In each case the ramp rate magnitude should be within ±2% of the programmed value.

4.2.7 Offset Control Accuracy

• Ground both the Measure and Setpoint inputs of the SIM960 using either BNC grounding caps or 50 Ω terminators.

• Reset the SIM960 using *RST.

• Turn oﬀ P control using PCTL OFF.

In each case, the output display value should be within ±5 mV of the programmed oﬀset.

4.2.8 Manual Output Accuracy

In each case, the output display value should be within ±5 mV of the programmed manual output value.

4.3 Calibration

• Turn on Oﬀset control using OCTL ON.

• Change the Oﬀset value to 0.000 V, +8.000 V, and −8.000 V, us-

ing the OFST command, and observe the ’Output’ display at each level.

• Reset the SIM960 using *RST.

• Select Manual output using AMAN MAN.

• Use the MOUT command to change the manual output level

to 0.000 V, +8.000 V, and −8.000 V, and observe the ’Output’ display value for each level.

If any of the preceeding tests fail, the SIM960 should be returned to the factory for recalibration. Contact Stanford Research Systems or an authorized representative before returning the SIM960.

SIM960 Analog PID Controller

5 Parts Lists and Schematics

This chapter presents a brief description of the SIM960 circuit design. A complete parts list and circuit schematics are included.

In This Chapter

5.1 Circuit Descriptions . . . . . . . . . . . . . . . . . . . 5 – 2

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

5.1.2 Front Panel Display . . . . . . . . . . . . . . . 5 – 2

5.1.3 Input Ampliﬁer . . . . . . . . . . . . . . . . . . 5 – 2

5.1.4 Proportional–Integral–Derivative . . . . . . . . 5 – 3

5.1.5 Output Circuitry . . . . . . . . . . . . . . . . . 5 – 3

5.2 Parts Lists . . . . . . . . . . . . . . . . . . . . . . . . . 5 – 4

5.2.1 Digital Board & Front Panel . . . . . . . . . . . 5 – 5

5.2.2 Analog Board . . . . . . . . . . . . . . . . . . . 5–6

5.3 Schematic Diagrams . . . . . . . . . . . . . . . . . . . 5 – 7

5 – 1

5 – 2 Circuitry

5.1 Circuit Descriptions

The SIM960 consists of three separate printed circuit boards: the digital board, the front-panel board, and the analog board. The digital board is directly beneath the left-hand cover (as viewed from the front of the module).

Pages 1–3 of the schematics correspond to the digital board. Page 4 is the front-panel board, and pages 5–9 are the analog board.

5.1.1 Microcontroller

The SIM960 is controlled by microcontroller U103. It is clocked at 10 MHz by the oscillator built around U102, which will track the reference +REF 10MHZ signal (if present) on JP103.

5.1.2 Front Panel Display

The front panel display is illuminated by successively strobing eight digital lines from U301. Each strobe line consists of an NPN emitterfollower (Q301 through Q308) that energizes one seven segment display chip and a set of eight LEDs in parallel. The eight cathodes from the segment display are held high or low at U302 based on a pattern from the controller. Similarly U303 controls the eight lines from the LED cathodes, using NPN open-collectors (Q309 through Q316) as output current buﬀers.

5.1.3 Input Ampliﬁer

The Measure and Setpoint single ended inputs of the SIM960 are diﬀerenced to form the error signal, ε, with a standard three op-amp instrumentation ampliﬁer (U512, U513), operating at 9× gain. R544, R549, R553, & R558 are high-stability resistors (0.1 %, 5 ppm/◦C), used to reduce oﬀset drift and to improve common mode rejection (CMRR). R550 is a 10 Ω trimpot for trimming the CMRR.

Polarity control is implemented at U514, which switches between gain +1× and −1× with U501A.

Next, U505B is a 12-bit multiplying D-to-A converter (DAC), which together with U504 is used as a vernier attenuator in the error ampliﬁer. Finally, there are three inverting ampliﬁers in series, each of which may be switched between gain −1×and some larger gain. The three ampliﬁer gains (−16×, −4×, and −2×) allow the total ampliﬁer gain to be switched by factors of two up to approximately 128×. The order of the ampliﬁers, largest ﬁrst, is intended to optimize noise referred to input.

SIM960 Analog PID Controller

5.1 Circuit Descriptions 5 – 3

5.1.4 Proportional–Integral–Derivative

The resulting ampliﬁed error signal P × ε (inverted at this point) is then distributed to the three paths, P, I, and D (see schematic page

6). The P path is unchanged, while the other two paths, I and D, each use 12-bit DACs (U606A and U606B) for vernier attenuation of the I and D gains.

Integral action is achieved using a multiplexed feedback capacitor design. U602 is addressed to choose one of four capactors, all of which are parallel to the ﬁxed feedback capacitor C643, whose small capacitance sets the maximum integral gain value. A similar switching method is employed in the derivative path to choose the input capacitance of the diﬀerentiating ampliﬁer U609B. Note R617, which limits the maximum derivative gain to just over +40 dB.

Each of the three signal paths, P, I and D, passes through an analog switch (U601A, U601B, and U601C, respectively) before being combined at the summing junction, theinverting input of op-amp U605B. These switches allow individual signals (P, I or D) to be switched on or oﬀ at the summing junction. Manual oﬀset control also enters the summing junction, though no switch is used since zeroing the oﬀset circuit (U610 with U611) is equivalent to switching out the oﬀset signal. Note that R643 is placed in series with the feedback resistor R615 in order to roughly match the switch resistance of each of the switches in U601.

5.1.5 Output Circuitry

U807 is used to switch the ouput of the SIM960 between Manual and PID modes. The signal then passes through two cascaded diode limiter circuits.

D801 and D802 clamp the output signal with respect to the upper limit voltage generated by U508A, together with U509B and U509C. The eﬀect of cascading two diode limiter circuits is to narrow the clamping range by roughly a factor of two, down to about 100 mV. Comparator U805 switches high when the output signal (going into the limiter circuit at R823) exceeds the upper limit voltage. The inverting input ofU805 is referenced to the upper limit voltage through the divider combination R844 and R845, eﬀectively shifting the saturation turn-on location with respect to the clamping “knee”. The lower limit clamp is similarly implemented by D803 and D804.

The output of the limiter circuit is buﬀered by a composite ampliﬁer consisting of U821 and U822. This arrangement provides the driving capability of the LT1010 without suﬀering its large input oﬀset voltage, since the output of U822 is servoed to the noninverting input to

SIM960 Analog PID Controller

5 – 4 Circuitry

U821 via the feedback resistor R819. U823 is a photo-MOS switch that remains oﬀ during power-up until

the ±15 V rails reach about ±13 V. By then, the output of the Manual DAC, which is driving the SIM960 output during power-up, will have settled to near ground level and may be passed on to the output connector BNC without large start-up transients. Until switch U823 closes, the SIM960 output is referenced to ground via R863 (100k).

U820A provides a buﬀered analog output of the P × ε signal at the back panel of the SIM960. Also, the output of U731A is passed to the back panel to provide an analog output of the internally generated setpoint signal.

5.2 Parts Lists

The parts list for the analog board is separate from the digital & front-panel boards.

SIM960 Analog PID Controller

5.2 Parts Lists 5 – 5

Part Reference SRS P/N Value Part Reference SRS P/N Value

C102 5-00366-100 18P R220,R221,R222,R223,R224, 4-01136-110 1.58K C104 5-00376-100 120P R225,R226,R227 C105 5-00368-100 27P R228 4-01244-110 21.0K C107,C108,C110 5-00102-030 4.7U R232 4-01117-110 1.00K C116,C117,C118,C216,C220 5-00387-100 1000P R234,R236,R238,R240,R275 4-01146-110 2.00K C119 5-00345-090 4.0-34P R243,R248,R259 4-01184-110 4.99K C201,C202,C203,C204 5-00466-120 .1U R249,R250,R254,R255 4-01243-110 20.5K C301,C221 5-00318-110 2.2U/T35 R251,R260,R270,R271,R272, 4-01242-110 20.0K C222 5-00522-110 47U/T R273 C227,C228 5-00375-100 100P R257 4-01211-110 9.53K C241,C233 5-00367-100 22P R262,R263 4-00925-110 10 C240 5-00454-120 .01U R274 4-01670-121 20K 1% 2PPM D101,D102,D464,D465,D466, 3-00945-143 BAT54S R280,R277 4-01280-110 49.9K D467,D468,D469,D470,D471 R283,R285 4-01288-110 60.4K D201,D202,D203,D204 3-01430-143 BAS40-05 R284,R287 4-01088-110 499 D205 3-01409-145 BAV99DW R288,R289 4-01271-110 40.2K D401-D420, 3-00424-060 GREEN R301,R302,R303,R304,R305, 4-01459-100 150 D421,D422,D424,D427,D428, R306,R307,R308 D429-D443, R309,R310,R311,R312,R313, 4-01462-100 200 D444,D445,D446,D448,D449, R314,R315,R316 D450,D451,D452,D453,D454, R319,R321,R323,R325,R327, 4-01496-100 5.1K D455,D456,D457,D458,D459, R329,R331,R333 D460,D461,D462 S401,S402,S403,S404,S405, 2-00053-000 B3F-1052 D426,D447,D463 3-00425-060 RED S406,S407,S408 JP101 1-00302-010 6 PIN DIF CES U101 3-00903-124 MAX6348 JP103 1-00367-040 15 PIN D U102 3-01378-103 74HCU04 JP104 1-00086-002 3 PIN SI U103 3-01379-114 68HC912B32 J202 1-01014 30 PIN 3x10 F U104 3-00662-103 74HC14 J301 1-00593-009 HEADER_SIL26 U201,U202 3-01380-120 LF444CM J401 1-00594-019 HEADER_SIF26 U203,U212 3-00731-120 5534 L102,L103,L105 6-00174-051 BEAD U204 3-01386-122 DG408 L301 6-00236-130 BEAD U205 3-01425-170 LTC2415CGN Q201 3-00927-150 MMBT2907ALT1 U206 3-01383-123 REF02 Q301-Q316 3-01421-150 MMBT2222 U207 3-00663-103 74HC08 R101 4-01495-100 4.7K U208 3-00116-030 78L05 R102,R106 4-01479-100 1.0K U209 3-00952-120 OPA2277 R103 4-01431-100 10 U210 3-00727-121 LM339 R105 4-01511-100 22K U211 3-00724-120 LF353 R107 4-01057-110 237 U213 3-00728-121 LM393 R109 4-01405-110 1.00M U301 3-01433-103 74HC259 R110,R116,R120,R121,R318, 4-01455-100 100 U302,U303 3-00751-103 74HC574 R320,R322,R324,R326,R328, U401 3-01424-061 HDSP-A107 R330,R332 U402,U403,U404,U405,U406 3-00290-061 HDSP-A101 R111,R114,R118,R123,R151, 4-01503-100 10K R152,R153,R154,R155,R276, X101-X314 (41 total) 5-00299-100 .1U R334 Y101 6-00571-020 10.000MHZ R112,R113,R122 4-01527-100 100K Y104,Y108,Y202,Y203,Y204, 4-01213-110 10.0K R115,R117,R119 4-01465-100 270 Y206,Y207,Y208,Y210,Y211, R128,R242 4-01309-110 100K Y229,Y252,Y253,Y256,Y258, R201,R205,R209,R212,R233, 4-01405-110 1.00M Y261,Y282,Y283,Y284,Y285 R235,R237,R239,R282,R286 PCB, SIM960 Digital Board 7-01258

5.2.1 Digital Board & Front Panel

SIM960 Analog PID Controller

5 – 6 Circuitry

Part Reference SRS P/N Value Part Reference SRS P/N Value

C502,C504,C506,C507,C536, 5-00365-100 15P R702 4-01050-110 200 C537,C538,C541,C608,C637, R704 4-01195-110 6.49K C638 R708 4-01287-110 59.0K C511,C521,C618,C708,C816 5-00369-100 33P R711,R712,R719,R720,R761, 4-01088-110 499 C602,C702,C832 5-00026-100 22P R803,R809,R811 C603,C616,C712 5-00072-050 10U R723,R724,R725,R726,R740, 4-00218-000 10.00K C610 5-00025-100 100P R744,R866 C611 5-00442-120 .001U R746 4-00011-053 10K C612 5-00454-120 .01U R748 4-00014-053 5K C613 5-00466-120 .1U R748 4-00014-053 5K C614 5-00538-050 1.0U R760 4-01128-110 1.30K C640 5-00350 .56U R763,R762 4-01021-110 100 C641 5-00582 .033U R764 4-01169-110 3.48K C642 5-00048-050 .0015U R765 4-01455-100 100 C643 5-00583 100P R804,R812 4-01551-100 1.0M C740 5-00059-051 .47U R808,R810,R814,R815 4-01486-100 2.0K C741,C742 5-00098-030 10U R817,R826 4-01111-110 866 C811,C821,C903,C904,C906 5-00102-030 4.7U R821 4-01038-110 150 C834 5-00377-100 150P R837,R840,R842 4-00913-000 49.9 FP D802,D801 3-01430 BAS40-05 R844,R847 4-01142-110 1.82K D804,D803 3-00901-145 BAS40-06 R863 4-01309-110 100K D808,D807 3-01487 12V zener R865,R864 4-00219-000 20.00K J505,J506,J701,J804,J805 1-00073 Insulated BNC U501 3-01358-122 DG444 J901 1-01015 30 PIN 3x10 M U504,U506,U513,U605 3-01361-120 OPA2228 K502 3-00308-203 DS2E-ML2-DC5V U505,U508,U606 3-01363-171 LTC1590 Q504,Q505,Q802 3-00927-150 MMBT2907A U509 3-01364-120 OPA4277 Q801 3-01421-150 MMBT2222 U514,U512 3-01360-120 OPA228 R502,R507,R542,R547 4-01175-110 4.02K U601 3-01365-122 DG411DY R510,R533,R534,R819 4-01146-110 2.00K U702,U602 3-01366-122 DG333ADW R527 4-01158-110 2.67K U603,U604,U807 3-01367-122 DG419DY R528 4-01149-110 2.15K U701,U607 3-01398 OPA2131 R530 4-01204-110 8.06K U608 3-01386-122 DG408DY R531 4-01262-110 32.4K U609 3-01361-120 OPA2228 R535,R536,R538,R539,R641, 4-01242-110 20.0K U610 3-01431 LTC1595 R642,R816,R829 U611,U708,U720,U809 3-00952-120 OPA2277 R541,R566 4-00012-053 20K U703 3-01369-122 DG409/SO R544,R549,R553,R558 4-01649-000 1.000K U808,U707 3-01372-171 LTC1596-1 R545,R556,R710,R839,R860 4-01405-110 1.00M U709 3-01374-103 74HC132A R548 4-01418-100 3 U710 3-00742-103 74HC74 R550 4-01614-053 10 U711 3-01375-103 74HC86 R551,R617,R709,R713,R721, 4-01117-110 1.00K U712,U802,U803,U805 3-00813-121 LM311M R862 U823,U730 3-01488 AQY221R2S R557,R554 4-01067-110 301 U731 3-01387-120 LT1097S8 R559,R563,R564,R565 4-00925-110 10 U732 3-00133 OPA131 R560,R561,R562,R718,R747, 4-01184-110 4.99K U804 3-00744-103 74HC151 R806,R813,R823,R824 U820 3-01370-120 OPA277UA R602,R614,R615,R619,R628, 4-01163-110 3.01K U821 3-00998-120 OPA227UA R845,R846 U822 3-00279-340 LT1010CN8 R616 4-01317-110 121K U901 3-01432 OPA4131 R618,R620,R621,R622,R623, 4-01561-100 2.7M U903,U902 3-00787-103 74HC595 R624,R717,R805 X509-X910 (90 total) 5-00299-100 .1U R644,R643 4-00997-110 56.2 Y537-Y827 (16 total) 4-01213-110 10.0K R645,R646,R647,R648 4-01503-100 10K PCB, SIM960 Analog Board 7-01259

5.2.2 Analog Board

SIM960 Analog PID Controller

5.3 Schematic Diagrams 5 – 7

5.3 Schematic Diagrams

Schematic diagrams follow this page.

SIM960 Analog PID Controller

Stanford Research Systems SIM960 Operator Manual

Specifications and Main Features

Frequently Asked Questions

User Manual