Equipment information
Clark Hess Communication Research Corp 255 Digital multimeter
Manufacturer:
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Model:
255
Date:
1983
Category:
Group:
Description:
VOLT-AMPERE-WATT METER
Information
The Model 255 digital V-A-W meter provides TRUE RMS
measurements of VOLTAGE, CURRENT, and POWER. These
measurements are essentially independent of the waveshape
and of the power factor from DC up to frequencies of hundreds
of kilohertz. Voltage and current readings are typically
within 1°/o
to 400 kHz for sine waves. The power in a 100 kHz square wave
may normally be measured within 2%.
WIDE MEASUREMENT RANGE
AMPLE RESOLUTION
The Model 255 provides FOUR full scale current ranges from
5 mA to 5 A, THREE full scale voltage ranges from 20 V to 1000
V., TWELVE full scale power ranges from 100 mW to 5000 W
and TWELVE, increased resolution POWER X10 ranges from
10.00 mV to 500.0 W.
A full four digit display provides ± 1 digits of resolution
for full
scale ranges corresponding to 1000, 2000, or 5000 digits.
ISOLATED OUTPUTS AND PROGRAMMING
The meters have optically isolated, digital options of:
A. Parallel, four digit BCD output
B. Remote control of FUNCTIONS
C. IEEE-488 Talker/Listener Board.
The meters have an optional isolated ANALOG output. One
volt output for a Full Scale display reading.
CURRENT OR VOLTAGE RANGE EXTENSION
Full Scale CURRENT ranges down to 50.00 pA or VOLTAGE
ranges down to 1.000 V or 2.000 V are possible. External broad
band shunts or transformers allow CURRENT extension to
50.00 A or 500.0 A. External voltage dividers allow VOLTAGE
extension to 3500 V. Full Scale POWER for each case is equal
to the VOLTAGE X CURRENT product.
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DEALS WITH MANY
DIFFICULT MEASUREMENTS
The Model 255 is ideally suited to measuring almost any non-
sinusoidal and/or low power factor waveshape. Typical uses are
in connection with SW ITCHING POWER SUPPLIES,
TRANSFORMER LOSSES, FLUORESCENT LAMP
BALLASTS, R-C Filter RECTIFIER CIRCUITS, SCR CIR
CUITS, MERCURY-ARC LAMP CIRCUITS, SERVO
SYSTEMS, MOTOR TESTING, ULTRASONICS, MOV LOSS
TESTING, AUTOMATIC TEST EQUIPMENT, SODIUM LAMP
BALLASTS, FERRITE CORE LOSSES, TELEVISION SET
LOSSES, AND ELECTRIC AUTOMOBILE EFFICIENCY
MEASUREMENTS.
EASY TO USE/HARD TO DAMAGE
The Model 255 is an all solid state, digital readout instrument.
The V-A-W meter is complete, self contained instrument that is
easy to use, hard to damage, easy to service, and easy to
maintain.
LOW CIRCUIT LOADING
An imput impedance of five Megohms for the VOLTAGE
terminals coupled with a full scale voltage drop of 100
millivolts
across the CURRENT terminals cause negligible circuit loading
or errors in most practical cases.
PACKAGING/PROTECTION
The Model 255 is housed in a heavy duty aluminum case. The
three lowest current range shunts are also diode and fuse
protected.
Manual Type:
Service and User Manual
Pages:
98
Size:
3.30 Mbytes (3457534 Bytes)
Language:
english
Revision:
Manual-ID:
255-2940
Date:
1983 01 01
Quality:
Scanned document, all readable.
Upload date:
2017 04 16
MD5:
0d1dd1738aa41251a8ae21bd121f08d5
Downloads:
334
Information
WARRANTY
LIST OF ABBREVIATIONS AND CONDENSATIONS USED IN THE MANUAL
SPECIFICATIONS
I. BASIC FEATURES, CONTROLS, AND CONDENSED OPERATING
INSTRUCTIONS
1-1.
Introduction
1-2
Basic Controls, Inputs and Outputs
1-3
Special Features
1-4
Condensed Operating Instructions - Voltage and Current
1-5
Condensed Operating Instructions - Power
1-6
Condensed Operating Instructions - Power Factor
1-7
Three Phase Power Measurements
II. CALIBRATION : MEASUREMENT AND ADJUSTMENT
2-1
Calibration Equipment and Standards
2-2
Calibration Measurement - Zero
2-3
Calibration Adjustment - Zero
2-4
Calibration Measurement - Current
2-5
Calibration Adjustment - Current
2-6
Calibration Measurement « Voltage
2-7
Calibration Adjustment - Voltage
2-8
Calibration Measurement - Power
2-9
Calibration Adjustment - Power
2-10
Calibration Measurement - Power Factor
2-11
Calibration Adjustment - Power Factor
III. THEORY OF
OPERATION
3-0
General Operation
3-1
Current Attenuator Board
3-2
Voltage Attenuation Board and Box
3-3
Display Board
3-4-0
Analog Section - General
3-4-1
Amplifier/Multiplier/Input CMOS Switches
3~4-2
Auto-Zero Circuitry (Amplifier/Multiplier)
3-4-3
Analog/Digital Conversion
3-4-4
Power Factor Detector
3-4-5
Square Root Generator
3-4-6
Input Overload Detectors
3-5-0.
Clocks and Timing - General
3-5-1.
Low Frequency Clock, LFC
3-5-2.
High Frequency Clock, HFC
3-5-3.
Active
3-5-4.
Signal
3-5-5.
Reference
3-5-6.
Load Latch Pulse, LL, and NOT LL
3-5-7.
Polarity Signals
3-6-0.
Digital Control Circuitry
3-6-1.
Decimal Point, Function, and Full Scale Memories
3-6-2.
Input Decoding Circuitry
3-6-3.
Drivers for the CMOS Switches in IC11, 12, and 13)
3-7.
"Dynamic" Switch Drivers
3-8-0.
Over and Under Range Circuitry
3-8-1.
Output Over Range
3-8-2.
Input Under Range
3-9-0.
Power Supplies
3-9-1.
+5 V Supply
3-9-2.
± 15 V Supplies
3-9-3.
+8 V and -6 V Supplies
3-10.
Options, including IEEE-488 bus, analog output, and
range extension.
IV. REPAIR AND
ADJUSTMENT
4-0.
Introduction
4-1.
Power supply Voltages
4-2.
Input Protection
4-3-1.
Analog Section - General
4-3-2.
Auto-Zero
4-3-3.
Integrator/Comparator
4-4.
Clock and Timing Circuitry
4-5.
Digital Control Logic/Specialized Circuits
4-6-0.
Adjustment Procedure After IC Replacement in the
Analog Section
4-6-1.
Input DC Offset Controls, P2, 12, and 130
4-6-2.
Multiplier Crossover Controls
4-6-3.
Multiplier DC Offset Controls
4-6-4.
Multiplier Linearity
4-6-5.
Other Controls
V.
REPLACEMENT PARTS
VI. DIAGRAMS