Equipment information:

Electro Scientific Industries 242D Level Meter
Electro Scientific Industries
Model: 242D
Date: 1971
Category: Measurement instruments
Group: Level Meter
                                    The Model 242D Resistance Measuring System provides the
facility for making precision resistance
measurements and comparing resistance standards . When used
in conjunction with a set of Model
SR 1010 Resistance Transfer Standards, the system can be
used for accurately comparing different
value resistance standards. For example, a 10 kilohm
certified standard can be used for checking
a 120 ohm resistor to an accuracy of a few ppm. The Model
242D is a major part of the equip­ment necessary for
calibrating voltage dividers to highest accuracy.
The system consists of ESI Models 240C Kelvin Ratio Bridge,
RS 925D Decade Resistance Standard,
and 801 D C Generator-Detector. The value of the unknown
resistor is read as the product of a
decade reading and a multiplier reading. A deviation dial is
also provided for reading the dif­ference between the actual
ratio and the nominal ratio of the standard and unknown
resistors in
parts per million or percent.
The Model 240C Kelvin Ratio Bridge is a four-terminal
comparison bridge using a modification of
the Kelvin double-bridge circuit. The bridge has
four-terminal connections to eliminate test
lead resistance in series with the unknown , It uses
switches and terminals designed to minimize
insulation leakage in parallel with the unknown. Front-panel
controls allow lead and yoke ad­justment as part of the
measurement cycle. All ratios are adjustable with
narrow-range trimmers
so that the bridge can be maintained with its initial
accuracy indefinitely.
The Model RS 925D Decade Resistance Standard provides
resistance values from 10 milliohms to
1.2 megohms in 100 microhm steps, The usual zero resistance
problem is eliminated by not going
below 10 milliohms. The lead and contact resistances are
included in the 10 milliohm resistors
so that the- resistance “the bridge—'-sees" is the same as
the dials read. Four-terminal connection
to the bridge avoids lead and contact resistance problems
between the units. The first four de­cades of the resistance
standard have narrow-range trimmers on each step so that the
standard can
be adjusted for very high accuracy at all steps.
The Model 801 D C Generator-Detector provides an optimum
signal source and null detector com­bination for the Model
242D System. Six generator voltage-resistance combinations
are avail­able for matching the generator to the bridge
input over a wide range of measurement values. To
protect the bridge and the components being measured, no
more than one watt can be supplied to
the bridge with each voltage-resistance combination. The
Model 801 has maximum protection
from hum pickup. Provision has been made for operation by an
external switch .

These manuals are available for the above equipment:

Electro Scientific Industries -- 242D -- Service and User Manual
File name: ESI-8025-Manual-Page-1-Picture
Manual Type: Service and User Manual
Pages: 125
Size: 3.65 Mbytes (3831900 Bytes)
Language: english
Manual-ID/Number: 19625
Date: 01 June 1971
Quality: Scanned document, reading partly badly, partly not readable.
Upload date:
MD5: 67a37d87c33e59cac7d6f01b70af3b78
ed2kID: 513ba6742c0329d444f0db5736628477
Downloads: 16 since 11 September 2016
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