Equipment information

Keithley 155 Digital multimeter
Manufacturer
Keithley
Model 155
Date 1978
Category Measurement instruments
Group Digital multimeter
Description Null Detector / Microvoltmeter
Information
                                    GENERAL

The Keithley model 155 is a completely solid state, rugged,
battery-operated combination Null Detector-Microvoltmeter.
It measures from 1 microvolt full scale to 1000 volts in 19
Ix and 3x steps and has 150 nanovolts resolution. The
recorder output, accurate to 1% of full scale exclusive of
noise and drift, extends the versatility of the instrument.

FEATURES.

a.	Excellent immunity to ac interference allows the Model
155 to detect dc signals in the presence of large ac
voltages. The Microvoltmeter, Null Detector has greater than
14 0 dB CMRR and 10 0 dB HMRR {refer to specifications in
Table 1). Also, hook up to source is simple and quick.
Unshielded leads may generally be used without degrading
performance.

b.	The model 155 Null Detector can recover from 100-volt
overloads within 5 seconds on the 30-micro-volt range. Up to
1200 volts peak may be applied momentarily on any range
-without damaging the instrument .

c.	Stability is better than 0.5 microvolt per 24 hours after
warm-up with a reasonably constant ambient temperature. The
long-terra drift is non-cu-mulative.

d.	The ten-turn EERO Control permits easy adjustment of
instrument zero. It also provides up to at least -25
microvolts suppression, ’which allows measuring submicrovolt
changes in signals up to the limit of the suppression.

e.	Zero Check position on the Power Switch allows convenient
zeroing of the instrument by shorting the input. This means
the measuring circuit need not be disturbed by
disconnecting' and shorting the input cables.

f.	High input resistance of 1 to 100 megohms coupled with
less than 10"-^ volt per ohm zero shift with source
resistance permits measurement accuracy even with high
resistance sources.

g._ The model 155 is designed for battery operation to
minimize ground loop and high frequency pick-up problems in
sensitive voltage measurements. Four internally mounted
zinc-carbon batteries provide greater than 1000 hours
operation. The Model 15 5 may also be operated from external
supplies. These may be connected to the barrier strip on the
rear panel. Power requirement is ±15 to ±25 volts at 2
milliamperes.

h.	For line operation, the Model 1554 Power supply is a
convenient accessory. It attaches to the rear panel of the
instrument and its output may be
connected to the barrier strip provided also on the rear
panel. A switch on the supply provided selectable line or
battery operation. Line operation with the Model 1554
maintains excellent floating characteristics and negligible
coupling to line.

i.	Four binding posts on the front panel provide fast and
convenient input connection. A ±1 volt at 1	milliampere
output is provided on the rear panel for convenient
connection to recorders or other readout devices. Accuracy
is ±2% of full scale at the meter and ±1% at the recorder
output. A large 4-1/2 inch taut-band meter is provided for
ease of readout.

j. The model 155 is completely solid state, utilizing a
MOS-FET chopper in its input circuit. The solid-state
chopper requires little power to drive, which gives long
battery life and permits the use of inexpensive batteries.
It also has low noise and increased sensitivity.

k. Another significant design characteristic of the Model
155 is its electrical and mechanical ruggedness. All
components except for the meter, battery, input and output
connectors are mounted on a single printed circuit. For
calibration or servicing the circuit board, may be
conveniently and quickly removed from the instrument.

l.	Circuit isolation from chassis ground is greater than 10
ohms shunted by 0.01 microfarad. This high isolation
generally eliminates the need for guarding the model 155.

APPLICATIONS.

a.	As a null detector the Model 15 5 can be used with
potentiometers, bridges, ratio devices and comparator circuits.

b.	As a microvoltmeter it is ideal for measuring
semiconductor resistivity, thermopile and thermocouple
potentials, Hall-effect potentials, contact resistances,
biologically generated emfs, electrochemical potentials, and
strain gauge outputs.

c.	Other applications include monitoring Power supply
stability, DTA measurements, resistance thermometry and
thermal conductivity measurements.

d.	The Model 15 5 is useful as a general purpose instrument
in the research laboratory as well as in electronic
development work and process control applications .

e.	Its excellent sensitivity limits the need for expensive
potentiometer systems to measure microvolt level signals
accurately. It can measure a signal of 30 microvolts or less
as accurately as some complex potentiometer systems.

These manuals are available for the above equipment:

Manual Type Service and User Manual Keithley-11202-Manual-Page-1-Picture
Pages 38
Size 3.14 Mbytes (3293065 Bytes)
Language english
Revision
Manual-ID/Number
Date 01 July 1978
Quality Scanned document, all readable.
Upload date
MD5 6c4c99e2417cd57a6078ffe1b45fdbff
Downloads 85 since 19 August 2018
Information
SPECIFICATIONS-------------------------------------------------------------------------------iv

1.	GENERAL DESCRIPTION -----------
--------------------------------------------------------1

2.
OPERATION--------------------------------------------------------------------------------3

3.	CIRCUIT DESCRIPTION
------------------------------------------------------------------------------5

4.	SERVICING-----------_ _ -----------------.------------------8

5.
CALIBRATION------------------------------------------------------------------------------------12

6.
ACCESSORIES-----------------------------------------------------------------18

7.	REPLACEABLE PAKTS--------------
-------------------------------------------------21

SCHEMATICS-----------------------------------------------------------------------------29
Keithley-11202-Manual-Page-1-Picture


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