Gould 400 User Manual

Gould 400 Series Digital Storage Oscilloscopes Operators Manual

400 Operators Manual

Contents

Introduction

Getting Started

Advanced Features

The Menus

Performance Checking

Waveform Processing

Battery Unit Operat io n

Alphabetical Summary

Appendix 1 Error Messages

Appendix 2 Specification

Appendix 3 Remote Operation

ppendix 4 Front & Back

Pictures

Service Facilities

Contents

400 Operators Manual

Introduction

Getting Started

1.1 Safety and Power Requirements

1.1.1

International Safety Warning

1.1.2

Grounding

1.1.3

Live Parts

1.1.4

Ventilation and Dust

1.1.5

Operating Temperatures

1.1.6

Power & Frequency

Requirements

1.1.7

1.2 Using the Buttons

1.3 Start-Up Display

1.4 Obtaining a Trace

1.5 Horizontal Adjustments

1.6 Vertical Adjustments

Fuse Requirements

1.4.1

AUTO SETUP

1.4.2

Channel Selection (Off/On/lnv)

1.4.3

Coupling (AC/DC/Gnd)

1.5.1

TIME/DIVISION

1.5.2

Aliases

1.5.3

Position

1.5.4

Magnification

1.6.1

VOLTS/DIVISION

1.6.2

Position

1.6.3

Variable/Uncalibrated

1.6.4

Add

1.7 Manually Obtaining a Trace

1.8 Operating Hints

1.8.1

1.8.2

Advanced Features

2.1 Trigger Control

2.2 Captu e Facilities

2.3 Display Modes

2.4 Cursor Measurements

1.8.3

1.8.4

1.8.5

2.1.1

2.1.2

2.1.3

2.1.4 Slope

2.1.5

2.1.6

2.2.1

2.2.2

2.2.3

2.4.1

2.4.2

2.4.3

Intensities too low Trace off the top or bottom

Trace not being acquired Trace unstable Trace has flat top or bottom

Selecting Source and Coupling Level Trigger Point (T)

Trigger Mode (Norm/Auto) Trigger Delay

Trace Hold S/Shot and Run

Acquisition Status-AFTS

Cursor and Datum Selection

Making Measurements

of screen

(+/-)

The Cursor& Datum Lines

Plot

2.5

2.5.1

2.5.2

2.5.3

2.5.4

2.5.5

2.5.6

2.5.7

2.5.8

Internal Colour Plotter Pens

Pen Changing Paper Selection Paper Loading Internal plotting External plots Plot positioning and scaling

Data Transfer

2.6

2.6.1

2.6.2

2.6.3

Syntax Receiving Data Error Status

Real Time Clock

2.7

The Menus

Additional Buttons

3.1

3.1.1

3.1.2

3.1.3

3.1.4

The Numeric Buttons Menu Traces Control Post Store

Control Master Menu

3.2

Status Menu

3.3

3.3.1

3.3.2

3.3.3

3.3.4

3.3.5

3.3.6

Mode Max/Min V/Div Probe set Timebase Trigger

Display and Trigger Menu

3.4

3.4.1

3.4.2

3.4.3

3.4.4

3.4.5

Probe ratio Max/Min Dot Join Averaging

Trig Pos'n

Display Intensity

3.5

Reference Trace

3.6

RS423 Interface Menu

3.7

3.7.1

RS423 Plot Connections

3.7.2

RS423 Data Connections

Special Functions Menu

3.8

Post Store Master Menu

3.9

3.10 Save Trace Menu Recall Memory Menu

3.11

3.12 Plot Menu

Performance checking

Risetime

4.1

Bandwidth

4.2

Trigger sensitivity

4.3

Trigger bandwidth

4.4

Timebase calibration

4.5

Vertical Calibration

4.6

Max-Min (Alias Detector)

4.7

400 Series Operators Manual

Contents

Waveform Processing Functions

5.1 Cursor Measurements

5.1.1 Voltage and Time

5.1.2 Peak-Peak

5.1.3 Max-Min

5.1.4 Risetime (falltime)

5.1.5 Overshoot (preshoot)

5.1.6 Pulse Width

5.1.7 Frequency, Period, Duty Cycle

5.1.8 RMS

5.1.9 Area

5.2 Trace Manipulation

5.2.1 Filter Frequency

5.2.2 Filter Current Trace

5.2.3 Invert Current Trace

5.2.4 Integrate Signal

5.2.5 Integrate Current Trace

5.3 Trace arithmetic

5.4 Persistence/Limits Testing

5.4.1 Limits

5.4.2 Persistence

Battery Unit Operation

Alphabetical Summary of controls

Appendix 1: Error Messages

Appendix 2: Specification

Appendix 3: Remote DC operation of the DSO

Appendix 4: Front and Back Pictures

Service Facilities

Figure List

1.2a Single Function Buttons

1.2b The Toggles

1.2c

Pressure Sensitive Buttons

1.3

Start-Up Display

1.4

Obtaining a trace

1.4.1 An AUTO SETUP Display

1.5

Horizontal Controls

1.5.2 Alias Generation

1.6

Vertical Controls

2.1

Trigger Controls

2.1.6 Trace Capture with Delay

2.2

Capture Controls

2.4

The Cursor and Datum Line Controls

2.4.2 The Cursor and Datum Lines

2.5.5 Paper Loading

2.5.8a Relative Plot Positions

2.5.8b Plot Dimensions 3

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.7.1 400to Gould 6120 or HP7475 Connections

3.7.2a 400 to IBM-PC/XT Connections

3.7.2b 400 to IBM-PC/AT Connections

3.8

3.9

3.10 Save Trace Menu

3.11 Recall Trace Menu

3.12 Plot Menu

5.1a Cursor Measurements Menu

5.1b Example of Calculations on trace

5.1.1 Voltage and Time Measurement

5.1.2 Peak to Peak Measurement

5.1.3 Max-Min Measurement

5.1.4 Risetime Measurement

5.1.5 Overshoot Measurement

5.1.6 Pulse Width Measurement

5.1.7 Freq. Period and Duty Cycle Measurement

5.1.9 Area Measurement

5.2

5.4 6

6.2 A2 A3.2 DC Power Connections A4a

A4b

Menu Overview Numeric Buttons Control Master Menu

A Status Menu A Display and Trigger Menu Display Intensity Menu

Reference Trace Menu An RS423 Interface Menu

Special Functions Menu Post Storage Master Menu

Trace Manipulation Menu Persistence/Limits Testing Menu Battery Unit Interconnections Battery Unit Front Panel Indicators

400 Series Dimensions

Rear View RS423 Connections

400 Operators Manual

Introducti

Introduction

The Gould 400 series instruments are Digital Storage Oscilloscopes (DSOs). They include all the features expected of advanced modern oscilloscop es designed for the professional engineer, whilst retaining the userfriendliness essential for those learning to use such instruments for the first time.

The 400 range consists of three basic models; the 400 the 420 and the 450. All versions can be fitted with a battery unit which provides the instrument with a fully automatic built in Nickel Cadmium battery and charger which allows uninterrupted operation of the DSO in the even t of an AC supply failure and complete operation independent of an AC supply.

Obtaining a trace is especially simple - just connect the signal and press the Auto Setup button - the 400 does the rest. Having obtained a trace, readily accessible datum lines and a cursor make it easy to take automatic timing and voltage measurements directly from the display. On the 420 and 450 models, the waveform processing function increases the power of the cursor measurements in terms of both capture and post storage analysis and measurement functions.

The innovative use of ergonomically designed pressure sensitive push button controls provides a combination of precision and flexibility for ease of operation.

More advanced features of the 400 series include a comprehensive range of menu-controlled functions. For example, the Display and Trigger menu operates features such as the trigger delay and pre-trigger display functions. The pre-trigger display function allows the signal prior to the trigger point to be captured and displayed.

Three complete traces can be stored for future use and recalled to the display via the Save Trace and Recall Trace menus respectively. With the built in battery back up facility, these will be retained even when the instrument is switched off.

In addition to the above features, the 420 and 450 instruments have a built in 4 colour plotter and a battery backed Real Time Clock. This provides a simple and convenient method of obtaining permanent hard copy plots of the screen display. The plots will contain the date and time of acquisition together with the date and time of plotting.

The 450 has all the features of the 420 and has a signal bandwidth of 50MHz and an extra timebase range of 50ns/div.

umbers circled in the text refer to the controls shown

on the front panel picture in Appendix 3.

Getting Started 1.1-1.1.6

400 Series Operators Manual

1.1 Safety and Power Requirements

1.1.1 International Safety Warning (as required for I.E.C. 348 Cat I)

This instrument has been designed and tested in accordance with IEC publication 348, and has been supplied in a safe condition. This manual contains information and warnings which must be observed to keep the instrument in a safe condition. The instrument should not be switched on if it is damaged and it should not be used under wet conditions.

For the correct and safe use of this instrument it is essential that both operating and service personnel follow generally accepted safety procedures in addition to the safety precautions specified in this manual.

Whenever it is likely that safety-protection has been impaired, the instrument must be made inoperative and be secured against any unintended operation. Qualified maintenance or repair personnel should be informed. Safety protection is likely to be impaired if, for example the instrument shows visible damage or fails to perform the intended measurements correctly.

1.1.2 Grounding

THE INSTRUMENT MUST BE GROUNDED.

The instrument must be operated with a protective ground connected via the yellow/green conductor of the supply cable. This is connected to the instrument before the line and neutral connections when the supply plug is inserted into the socket on the back of the instrument. If the final connection to the supply is made elsewhere, ensure that the ground connection is made before line and neutral.

If the unit is disconnected from the AC supply, and powered from an isolated DC source or the internal battery unit, the unit will not be grounded. Independent provision must be made to maintain the case at a safe potential, by grounding the safety ground terminal on the DSO rear panel. The safety ground terminal is connected to the instrument case, to the ground of the input signals (outer of the BNC connectors), and also internally to the negative side of the DC supply.

WARNING: Any interruption of the protective ground

conductor inside or outside the instrument is likely to make the instrument dangerous. Intentional interruption is prohibited.

Signal connections to the instrument should be connected after the ground connection is made and disconnected before the ground connection is removed, i.e. the supply lead must be connected whenever signal leads are connected.

1.1.3 Live Parts

The instrument should not be operated with covers removed. The covers protect the user from live parts and

they should be removed only by suitably qualified personnel for maintenance and repair purposes.

WARNING: Removing the covers may expose voltages in

excess of 8000V at the side of the display tube; these may be present for up to one minute after the instrument has been disconnected from the power source.

1.1.4 Ventilation and Dust

The instrument relies on forced air cooling via a fan and ventilation slots. Adequate ventilation can usually be achieved by leaving a 75mm (3" gap) around the instrument.

The instrument should not be operated in dusty environments. If the CRT filter requires cleaning it can be easily removed by

pressing in its right hand edge as shown by the moulded arrow.

1.1.5 Operating Temperatures

The instrument is designed to be operated in an environment having an ambient temperature of between 0 and 50 degrees C, (0 to 45 degrees if the battery unit is fitted) and to operate with full accuracy between 15 and 35 degrees C.

Note: Direct sunlight, radiators and other heat sources

should be taken into account when assessing the ambient temperature.

The instrument may occasionally be subjected to temperatures between 0

and -10ºC without degradation of its safety.

1.1.6 Power and Frequency Requirement s

The instrument uses less than 85V A (200V A if battery unit fitted) and operates from line voltages of 90V to 130V, and 190V to 265V, at 45 to 400Hz. Under the extreme conditions of 90V and 45Hz, the instrument will still operate correctly even if there is a half cycle dropout in the line supply.

The instrument may be powered from a direct current supply in the range 12V to 33V. The unit cannot be damaged by applying power to both inputs simultaneously.

Before connecting the instrument to the supply, ensure that the rear panel AC supply voltage selectors are set to the appropriate voltage.

Access to the voltage selector can only be made if the AC supply connector is removed, and is by hinging open the panel connector from its top edge. The selector barrel can then be moved to the required setting. This same operation provides access to the AC supply fuse, which must be changed to suit the supply voltage as shown in table 1.1. 7.

The AC power connection is via a standard IEC, CEE 22 connector and the DC power input is via the supplied 0.25" spade connector (Gould part No. 457839.) See appendix 4 for polarity details.

400 Operators Manual

Figure 1.2a Single Function Buttons

Getting Started

Figure 1.2b The Toggles

Figure 1.2c The Pressure Sensitive Buttons

Getting Started 1.1.7-1.4.1

pply

400 Series Operators Manual

CAUTION: The negative DC terminal is connected to the

safety ground terminal and the instrument case. Care should be taken to avoid ground loops when, for example, the instrument is used in a vehicle and powered by that vehicle's supply.

1.1.7 Fuse Requirements

The fuse arrangement shown in table 1.1. 7 must be followed, and additionally in the UK, a 3A fuse (5A if the battery unit is fitted) should be fitted in the line supply plug .

Slow Blow Gould Su

Voltage Fuse Rating Part No Manufacturer/Type No

IEC (ULlCSA) DSO

230V 0.5A (0.6A) 457452 BeswickrrDC488,

115V lA (1.2A) 457454 BeswickrrDC488,

12VDC 5A (6A) 457979 HRC type

BATTERY UNIT

230V lA (1.2A) 457454 BeswickrrDC488,

115V 2A (2.5A) 457455 BeswickrrDC488,

Table

1.1.7

Fuse ratings

ested t

es.

Littlefuse/239, Schurter/FSP

Littlefuse/239

Schurter/FSP

Beswick/S505,

Wickman 19181

Littlefuse/239,

Schurter/FSP

Littlefuse/239,

Schurter/FS

1.3 Start-Up Display

When switched on with the POWER button will go through its automatic self-calibration sequence and then display information similar to that shown in Figure

Figure

1.3

Start-Up Displa

The trace is visible across the centre of the screen. At the top will be the sensitivity of the two input channels and the timebase speed. It any input is inactive, information for that channel will not be displayed.

Users with no previous experience of a DSO will find that the 400 responds like a conventional Real Time Oscilloscope while it is repetitively triggered, but in the absence of further valid triggers, it retains the last trace for continuous display.

(1)

the instrument

1.3.

Note: For different DC voltages, the DC fuse rating multiplied

by the voltage used should equal60W. e.g. at 30V a 2A

is required. For additional safety under extreme

fuse fault conditions, the DC fuse (HRC) type. This fuse should have a 1500A break capacity.

1.2 Using the Buttons

There are three types of buttons. The first type usually have only one function: when pressed, that one function will be

(

activated e.g. AUTO SETUP

The second type are toggles: each press of the button either switches something on or off e.g. Add next item in a sequence e.g. Off/On/lnv

1.2b. The third type are Pressure Sensitive: the effect caused depends

upon how hard the button is pressed. For example, a gentle

press of a Pos'n (8) button will move the trace slowly. If the

button is pressed harder, the trace will move more quickly. See Figure 1.2c.

24)

a high rupture current

see appendix 3

See Figure 1.2a.

(10) , or selects the

(13) . See Figure

1.4 Obtaining a Trace

1.4.1 AUTO SETUP

To display an input signal, connect it via either the CHI socket

See Figure 1.4

(9) or the CH2 socket (12) and press AUTO SETUP (24) .

Assuming you've applied a regular signal, say a 2kHz sinewave with an amplitude of perhaps 5V peak to peak, it will almost immediately be represented on the display. An example is shown in Figure 1.4.1.

It the display is very dim or has completely disappeared see section 1.8.1.

AUTO SETUP will attempt to arrange the display so that two

to five complete cycles appear, with the amplitude set so that the height of the trace is between two and five screen divisions. Also, it selects Auto trigger to ensure that the screen is frequently updated and a trace will be visible.

If signals are connected to both channels, the highest amplitude takes priority.

400 Series Operators Manual

Getting Started 1 .4.2-1 .5.1

Figure

1.4

Obtaining a Trace

1.4.3 Coupling (AC/DC/Gnd)

These buttons control the type of coupling between the input signal and the instrument. DC is the most generally applicable, and AUTO SETUP will normally set this control to DC, where possible. The input impedance is I M ohm in parallel with a capacitance of 28pF.

(14)

AC This is used to remove any DC component from input

signals. Suitable input signals (i.e. the bandwidth) are from 4Hz to 20MHz.

Gnd The input signal is internally disconnected from the inputs and

the amplifier grounded. A OV reference signal is displayed.

DC The input signal is directly coupled to the instrument so all

frequency components of the input signal will be displayed. The bandwidth will be from DC to 20MHz.

1.5 Horizontal Adjustments

Figure

1.4.1

n AUTO SETUP Display

1.4.2

Channel Selection (Off/On/lnv)

A channel may be switched on or off with its Off/On/Inv button. If the channel is on, its trace can be displayed in either normal or inverted mode.

Off The channel is deactivated. On The trace is a true representation of the input signal. Inv The input signal is inverted before being displayed. If

there is any DC component in the signal this will also be inverted and could cause the trace to disappear from the screen. Such an unwanted DC component can be removed by selecting AC coupling. Any vertical shift applied to the trace is not inverted. The trigger point remains at the same point on the waveform regardless of inversion.

(13)

Figure

1.5

Horizontal Controls

1.5.1

TIME/DIVISION

TIME/DIV

With a timebase of say 200/Ls, each horizontal screen division represents 200/Ls worth of signal. The timebase is shown near the top of the display - e.g. TB=200/Ls.

Assuming a 2kHz signal is applied as mentioned earlier, when the timebase is set to 500ms/div, an interesting phenomenon may appear: an 'alias'.

(33) These buttons control the sweep rate of the trace.

The timebase can be varied from 100ns/div to 50s/div in a I, 2, 5 sequence of values. The button marked 'ns' decreases the time/div, the button marked 'sec' increases the time/div.

Getting Started 1 .5.2-1 .6.3

400 Series Operators Manual

1.5.2 Aliases

An alias is a false image. The instrument is a digital oscilloscope and so takes frequent samples of the input signal in order to update the trace. Thus, if the signal frequency is higher than the sample frequency, one sample will be taken from a particular point on the waveform and the next sample may be taken from a point slightly further along on a subsequent cycle. It will then display the wave as being much slower than it really is. See Figure 1.5.2. This effect is only likely to occur if there are more than 100 cycles of waveform across the screen.

Figure

1.5.2

Alias Generation

There is a 'Max/Min' glitch detection feature which can be used to detect aliases. With dot join on, this usually results in a filled-in wave envelope being seen on the screen, indicating a high

frequency. See Section 3

are 20mV to 50V per division at the probe tip. See Section

3.4.1

If the Uncal light is on, then these buttons vary the

1.6.3.

sensitivity continuously. See Section

1.5.3 Position

Position (26) These buttons move all traces to the right or

left.

The position of the cursor (Section trace so it will move with the applied shift. With x-magnified

1.5.4),

traces (Section displayed on the screen. To bring it back into view use the CURSOR < > buttons

the cursor can be off the part of the trace

(5).

2.4)

is fixed in relation to the

1.5.4 Magnification

Mag (32) Switches horizontal magnification on or off When

switched on, a xl0 expansion is applied to any displayed trace, which will expand around the centre of screen. The timebase setting is adjusted to reflect the expansion.

The instrument displays 50 dots (samples) per screen division, each plotted dot value being obtained from the 512 byte acquisition memory. At an expansion of x 10. there are five dots per division.

1.6 Vertical Adjustments

Each channel has its own set of vertical controls. See Figure

1.6.1 VOL TS/DIVISION

V/DIV

(11) Adjusts the sensitivity of the instrument over discrete

calibrated ranges from 2m V to 5V per screen division in 1,2,5 steps. With a x10 probe the ranges

1.6.

1.6.2 Position

(8) These move their respective traces up and down

Pos'n

the display.

If Trace Hold is on (Section 2.2) or a S/Shot capture has been made, any part of the trace which was captured off-screen vertically will be shown by a horizontal line.

1.6.3 Variable/Uncalibrated

Var (15) When this is set to 'Uncal', the coarse setting of the

attenuator remains unchanged, but a variable attenuation is

004.

applied to the input signal in the range of 1 to with an initial setting of IV, the actual sensitivity of the channel could be set by this control to anywhere between I V and 2.5V per division. The V/DIV buttons are used to vary the uncalibrated sensitivity.

Thus,

Example screen display:

CH1 =5V Channel is set to a sensitivity of 5 Volts per screen

division.

CH2>20mV Channel 2 is uncalibrated and the attenuator is set to a

sensitivity greater than 20m V per screen division.

400 Series Operators Manual Getting Started 1.6.4 - 1.8.5

1.6.4 Add

Add (10) Displays the sum, or if one channel is inverted the

difference, of the input signals. The original traces disappear and the resultant trace is displayed as a Channel 2 trace.

1.7

Manually Obtaining a Trace

This subsection describes how to obtain a trace without using AUTO SETUP.

You may need to consult later sections of the manual as not all of the operating features have been discussed so far.

1. When switched on, the instrument will go through its

power-up sequence, checking the internal calibration.

2. Decide to which channel you are going to apply the

signal (CH1 or CH2).

3. Make sure the chosen channel is active by setting the

Off/On/lnv

4. Set the AC/DC/Gnd button

nel to Gnd.

5. If necessary, turn that channel's Uncal light out by

pressing Var once.

6. Make sure that horizontal mag is not selected. (32)

7. Adjust the TIME/DIV setting

5μs.

8. Set the display Mode (31) to Refr.

9. Set the TRIGGER Norm/Auto button

10. Use the CHl/CH2/Ext/Line button (17) to choose the

source for trigger signals.

11. Set the trigger coupling with the hf rej/AC/DC button.

(13) for that channel to On.

(14) for the chosen chan-

(15)

(33) to give a timebase

(20) to Auto.

(18)

12. If necessary adjust the position of the trace using the

Position and Pos’n buttons.

13. Ensure that Trace Hold (25) is not selected.

14. Select Run.

15. Apply the signal through a BNC connector to the chosen

CH input socket. (9) or (12)

16. Set the AC/DC/Gnd button

either DC or AC, as appropriate.

17. Adjust the gain of the chosen channel using the V/ DIV

buttons by pressing the Var button once.

18. Adjust the timebase setting using the TIME/DIV but-

tons.

19. If the display is unstable, adjust the trigger Level. (22)

1.8

Operating Hints

The following list gives some of the more commonly met problems in operating digital oscilloscopes, how to correct them, and a brief explanation of what was wrong.

(27)

(11) . For intermediate settings, set Uncal on

(33)

(26)

(8)

(14) for the channel to

(15)

You may need to consult later sections of the manual as not all of the operating features have been discussed so far.

1.8.1 Problem: Traces and Alphanumerics very dim or completely disappeared.

Intensities too low

- Press the control button menu, then press numeric button 3 to select the intensity menu. Further presses of numeric button 3 will increase the brightness of the alphanumerics on the display. The traces can now be intensified using numeric button I.

Note:- The display may not become visible until the numeric

button

1.8.2 Problem: Trace off the top or bottom of the screen. Too

much vertical shift

Input has large DC offset

1.8.3 Problem: Trace not being acquired.

Instrument in single capture mode

Trigger level incorrect

Trigger source on the wrong input

Trigger coupling on an unsuitable setting

Trace Hold on

Timebase on very slow acquisition

1.8.4 Problem: Trace is unstable even when triggered. Alias

Noisy input

Trigger on Auto

1.8.5 Problem: Trace has a very flat top or bottom.

Trace captured when off screen vertically and Pos’n shift has been used

has been pressed several times.

- correct with that channel's Pos’n buttons.

- AC couple input signal.

- Correct with Pos’n buttons.

- Use a less sensitive range.

- Press Run.

- Select Auto and DC trigger, then adjust the level

control until the trigger level indicator bars are lined up

with the centre of the trace.

- Change trigger source. (CH1, CH2, Ext, Line) (17)

- Change trigger coupling. (hf rej, AC, DC) (18)

- Release Trace Hold.

-Adjust TIME/DIV.

- Check for alias using Max/Min (glitch detection), and select a faster timebase range.

- Select hf rej trigger coupling. (18)

- Adjust trigger Level.

- With low frequency inputs (below 20Hz), Auto trigger

will initiate triggers overriding the input triggers. Select

Norm trigger.

- Use less sensitive V/DIV range when acquiring trace. (11)

- Re-position trace prior to capture.

(27)

(20)

(7) to get the control master

(8)

(25)

(33)

(22)

dvanced Features 2.1-2.1.5

2 Advanced Features

2.1 Trigger Control

Trigger facilities discussed here are controllable directly from the front panel. For the more advanced menu-controlled facilities see Section 3.4.

The power-down trigger setting will be retained on future

ower-up.

400 Series Operators Manual

Table

2. 1. 1

Useful Frequency Ranges

Types

Coupling

hfrej 10Hz to 15kHz AC 4Hz to 20M Hz

DC DCt020MHz

2.1.2 Level

The trigger level is the threshold at which the instrument will respond to potential triggers; the trace actually has to pass through the level indicated for a trigger to be valid. See Section

2.1.3.

The level is indicated on the display by two bars, one on each side. of the screen, and is adjusted by the level buttons. For an internal trigger the range is approximately divisions and on external approximately signal is AC coupled, the level bars will be offset from the actual trigger position on the screen by any DC offset present.

2.1.3 Trigger Point (T)

Input

Coupling

- 3V. If the trigger

+/-

(22)

Figure

2. 1

Trigger Controls

2.1.1 Selecting Source and Coupling

The lowest button in the TRIGGER section of the front panel selects the source of the trigger.

CH1/CH2/Ext/line

of trigger signals. When Ext is selected, the source is the

'EXT TRIG' socket (16) in the lower right corner of the

front panel.

Selecting line is meaningful only if the instrument is powered from the mains. Triggering is then from an internal pulse having a fixed phase relation to the mains voltage waveform. To change this phase relationship, use the trigger delay buttons. See Section 2.1.6.

(17) Steps through the possible sources

The trigger point is indicated on the display by a 'T' near the bottom of the screen underneath the trigger. An arrow next to the T indicates that the trigger point is off the screen.

2.1.4 Slope

A trigger is generated when the selected source signal passes through the chosen trigger level. This transition may be either on a rising or a falling edge. The rising edge is considered to be a positive slope and the falling edge a negative slope.

+/-

(19)This button selects positive

slope triggers.

2.1.5 Trigger Mode (Norm/Auto)

The trigger system operates in either Normal or Auto mode.

In Normal mode, display captures can only occur when a valid trigger input has been received.

In Auto mode, if no valid trigger has been received for some time the instrument will generate its own trigger and initiate a capture. This ensures that the screen is constantly updated irrespective of the input signal. However, if valid input triggers are received at a rate of 20Hz or more, the instrument will start all captures with these triggers and not generate its own.

Auto/Norm (20)This button selects which trigger mode the

instrument is operating in.

Trig'd

receiving valid trigger signals.

(+/-)

(+)

or negative (-)

(21) This LED lights up when the instrument is

hf rej/

AC/DC

(18) Steps through the available trigger cou-

pling options; hf rej is a 15kHz low-pass filter ('high frequency reject'). All the couplings can be used with any source except Line, with which the input coupling is not selectable.

400 Series Operators Manual Advanced Features 2.1.6-2.2.1

2.1.6

Trigger Delay

The amount of data which is acquired for display before or after the trigger is determined by the pre or post trigger delay selected, see figure 2.1.6. The value of this delay is shown in the bottom right hand of the trace display.

Pretrig This allows a section of the trace that occurred

before the trigger point to be included in the display. The amount of pre-trigger visible can be set with the front panel PreTrig/Delay buttons. set anywhere between 0% and 100% of screen width, in steps as small as 0.4%.

Trig Delay With this set, the oscilloscope will acquire a trace

following both the specified trigger and a specified delay. The amount of delay is shown beside the 7 key. Delay is controlled by the PreTrig/Delay keys. The size of the steps by which the delay can be incremented or decremented is controlled by the TIME/DIV keys, i.e., step size is 0.04 x the time/ div setting. This can be demonstrated by varying both the timebase and delay settings, while observing the last two lines of the Display and Trigger Menu (See section 3.4). Once set, the delay time remains the same regardless of the selected timebase range.

(23) Pre-trigger can be

(23)

2.2 Capture Facilities

The capture facilities allow the traces to be frozen.

Figure

2.2

The Capture Controls

2.2.1

Trace Hold

There are two ways to freeze the display: a single-shot capture whereby a full trace is acquired then frozen (Section

Figure 3.4a Trace Capture with Delay

Advanced Features 2.2.2-2.4.2

400 Series Operators Manual

2.2.2), or by pressing one of the buttons labelled Trace Hold.

Trace Hold:

(25) Freezes the relevant trace or traces the moment

they are pressed. A second press releases the trace( s).

2.2.2 Single Shot and Run

These buttons are used to set the instrument into either a captureand-freeze mode (S/Shot), or a free running continuous capture and re-capture mode (Run).

S/Shot

(30) Arms the instrument for a single-shot triggered

acquisition. The Arm'd light will be illuminated to show that the button has been pressed.

Arm'd

(29) Illuminates after the S/Shot button has been pressed;

it will stay lit until either a valid trigger has been received or until the Run button is pressed.

Stor'd

Run

(28) Illuminates on completion of a single-shot

acquisition. This is after the instrument has been Arm'd, triggered and a complete trace acquired. The light will stay on until the instrument is re-armed by pressing S/Shot again or Run is pressed.

(27) This button puts the instrument in continuous capture

mode: the instrument will automatically rearm itself after each capture is completed so that the display will be updated with each triggered sweep.

2.2.3 Acquisition Status - AFTS

These characters appear on the screen and can be used with the Arm'd and Stor'd lights to determine the 'status of the acquisition in progress.

A Stands for 'Armed'. F Indicates that the acquisition store has been filled with

enough pre-trigger information to be ready for a fresh acquisition.

T Stands for 'Triggered': the instrument has received or

generated a valid trigger; acquisition has begun.

S 'Stored': acquisition is complete.

2.3 Display Modes

socket input to control the Y (vertical) component. It provides an X- Y display of the data captured by the time base and trigger systems. The timebase should be set slow enough to capture the whole of the signal of interest. This mode is not available with magnified traces (Mag).

2.4 Cursor Measurements

The instrument allows you to take direct measurements from the screen display automatically, using inbuilt datum lines and cursor.

Figure

2.4

The Cursor and Datum Line Control

2.4.1 Cursor and Datum Selection

The cursor and datum lines are switched on or off using the Select Trace button.

Select Trace

2.4.2 The Cursor and Datum Lines

There are three lines, as indicated in Figure 2.4.2. Movement of them is aCH1eved using the DATUM and CURSOR buttons, as described below.

(4)

(4) Successive presses of this button places the

cursor and datum lines on to the displayed traces in turn. i.e. channel, channel 2, reference, off, channel etc. If any of the traces are not in use the lines skip to the next valid selection.

The following three display modes are directly selectable using the

Mode button.

Refreshed The instrument will imitate the style of a conventional

Roll This mode is like a chart recorder: the display scrolls from

(31)

realtime 'scope: the display is plotted from left to right as it is acquired.

right to left until a trace has been acquired. The scrolling effect is most noticeable on the slower timebase ranges. The rolling display is frozen by the trigger in S/Shot mode and is unaffected by trigger in Run.

X-V This mode allows the CH1 socket input to control the X

(horizontal) component of the trace, and the CH2

Figure

2.4.2

The Cursor and Datum lines

400 Series Operators Manual

dvanced Features 2.4.3-2.5.5

Dat Selecting this option on the Dat/Pos/Mag button (3)

allows the position of the datum lines to be controlled

using the DATUM buttons. (2)

DATUM

(5) Moves the cursor to the right and left along the trace.

Pos/Mag These selections on the Dat/pos/mag button

Pos This option on the Dat/Pos/Mag button (3)

Mag The vertical magnitude of the selected trace can be varied

2.4.3 Making Measurements

The instrument displays, at the bottom of the screen, the time and voltage difference between the intersection of the horizontal and vertical datum lines and the cursor.

The choice of points between which to make the measurements can influence the accuracy: while the measurements made will always be within the design limits, placement of the cursor at the desired position is easier at those points where the slope of the waveform is at its steepest. For example, on a standard sine wave, the most accurate measurements of wavelength are likely to be made if they are taken between two OV crossing points.

(2)

Used for moving the two datum lines. CURSOR

(3)

allow the DATUM buttons to control post storage position and magnitude. They can only be used with stored waveforms. Pressing menu button 1 (opposite the restore message) will cancel the effect of pos and mag on the selected trace i.e. the one with the cursor

X and Y shift to be applied to the trace on which the cursor is placed, using the POST STORAGE/ DATUM

keys. (2)

from X4 to XO.062, using the POST STOR- AGE/DATUM keys. displayed near the top centre of the CRT.

No horizontal magnification is available using this control, but x10 magnification may be applied to all stored traces using the horizontal mag button. See Section 1.5.4).

(2)

The magnification factor is

it.

allows both

The normal pen sequence is:

Pen No. Colou

1 Black 2 Blue 3 Green

4 Re

The pen holder is colour coded with this colour sequence. When pens are fitted in this order, trace 1, the border and all the alphanumerics are plotted in black, trace 2 in blue, the reference trace in green and the graticule in red. The cursor and datum lines and their measurements are plotted in the same colour as the trace to which they relate. The cursor colour also applies to the HPGL output on both the 420 and 450.

2.5.3 Pen Changing

Underneath the plotter lid at the front of the plotter there are two small blue buttons. The right hand button when viewed from the front of the OSO is the Pen change button, and the left hand one is the paper advance button.

CAUTION: When changing a pen, extreme care should

be taken not to damage any of the plotter mechanism.

NEVER

move the pen carriage by hand.

To change a pen, ensure that the instrument is switched on and

then proceed as follows:

1. Press the pen change button once. This rotates the pen

carriage and moves the carriage to the right hand side of the plotter.

2. Gently press the white grooved eject lever towards the

front of the instrument. The top pen will be ejected from the pen carriage and can be removed from the plotter.

3. Insert the tip of the new pen into the carriage guide hole.

Gently snap the other end of the pen into place.

4. When the pen has been changed, press the left hand

button - the paper advance button - and the carriage will move back to the left hand side ready for the next plot.

2.5

Plot

2.5.1 Internal Colour Plotter Operation

When the internal colour plotter is fitted to the 400 OSO, plots of the instrument's display can be sent to it by selecting internal on the Plot Menu, see section 3.12.

The internal plotter is automatically selected on power up if it is fitted. If required the plot output can be directed via the RS423 port to an external plotter by selecting RS423 on the Plot Menu, see section 3.12.

2.5.2 Pens

Only use Gould pens - part number 04101175 for a pack of 4; 1 of each colour.

2.5.4 Paper selection

Only use Gould paper - Part number 04101165 for a pack of 8

rolls. Other paper types may damage the mechanism.

2.5.5 Paper Loading

CAUTION: When loading paper, extreme care should be taken

not to force any of the plotter mechanism. paper through by hand, always use the paper advance button to prevent damage to the plotter mechanism.

1. With scissors, cut the end of the paper square.

2. Open the plotter cover by depressing the catch and

lifting the cover until it is fully open.

3. Remove the shaft from the paper cradle and if the plotter

has been used previously remove the plastic or cardboard tube from the shaft.

NEVER

pull

dvanced Features 2.5.6-2.5.8 400 Series Operators Manual

4. Insert the shaft through the paper roll and fit the roll into

the paper cradle.

5. Feed the paper from the top of the roll as shown in

figure 2.5.5 below and push it through the slot in the rear of the printer mechanism.

6. Press the paper advance button - the left hand blue

button at the front of the printer assembly - until the paper reappears at the front.

7. Feed enough paper through to pass through the top

cover, ensure that it is running around the mechanism smoothly and that it is straight.

7. Close the plotter cover and ensure that it latches shut.

Figure

2.5.5.

Paper Loading

2.5.6

Internal Plotting

When a plot is initiated, the Hold All lamp lights and the message "PLOTTING - PRESS PLOT TO ABORT" appears on the screen. After about 9 seconds the hold All lamp goes out indicating that the data has been transferred to the plot buffer and that the instrument can be used again. The plotting message will remain on the screen until the plot is complete when it will disappear.

In Auto Plot Mode, the instrument is re-armed after the plot data has been transferred to the plot buffer, but the front panel controls will remain in-active during plots.

If the plot button is pressed while the plot is in progress, the plot will be aborted. Any changes to the instrument status during a plot will have no effect on the plot as the data has already been transferred and stored in the plot buffer.

2.5.7 External plots

A plot of the display can be sent to an external plotter by

pressing the plot button @ . The parameters for the plotter

and the plot format can be set as described in section 3.7 and

3.12.

The display is held while a plot is in progress.

Plots can be aborted by a second press of the plot button. If the plot is aborted, the pen will be left in a random position and the external plotter may need to be reset to restore the pen to its start position.

2.5.8

Plot positioning and scaling

The output plot from the 400 has the relative positions shown in figure 2.5.8a. These may be shifted and scaled to position the plot exactly over a pre-defined grid using the following procedure with reference to figure 2.5.8b.

The sides of the pre-defined grid are X and Y, the exact positions of PI and P2 are found by calculating the dimensions A, B, C and D:

Measure the vertical dimension of the required grid, note this as Y.

Measure the horizontal dimension of the required grid, note this as X.

U sing these values of X and Y, A, B, C and D can be calculated as follows:

Measure and mark the exact positions of PI and P2 from the grid edges using figure 2.5.8b and the values obtained above.

The PI and P2 points can now be set on the plotter, refer to the plotter manual for details.

400 Series Operators Manual

Advanced Features

Figure 2.5.8a Relative Plot Positions

Figure 2.5.8b Plot Dimension

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