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To achieve the best results when using the T.C. mode of operation the user should ensure that the sensor
is in the same environment as the test load, and is not in any large air currents which may cause cooling
effects. The user should also note that to reduce the effects of drafts the temperature sensor has been
designed with a long thermal time constant, thus at least 20 minutes should be allowed for thermal
stabilization following any large change in ambient conditions or following handling of the sensor.
CAUTION!
The case of the sensor is electrically connected to internal circuitry in the ohmmeter. The
sensor should have no electrical contact with the load under test.
Voltage and Current Terminals
The four terminals on the front panel provide full 4-wire Kelvin measurement capability. The
CURRENT terminals provide the test current while the VOLTAGE terminals are used to monitor the
voltage drop across the load. Refer to Chapter 7 for more details on connections.
Zero Control
This potentiometer may be used to trim out any offset present on the display. See Chapter 7.
Open Circuit Voltage Switches
These paragraphs apply only to Models 4165 and 4165-1344. The OPEN CIRCUIT VOLTAGE
switches are used to select the desired maximum compliance voltage of the current source. This
function ensures "dry" measurements by clamping the open-circuit voltage at the CURRENT terminals.
For example, if the 20mV switch is depressed the voltage at the CURRENT terminals will not exceed
20mV (±5%). These two switches are interlocked such that only one may be depressed at any one time.
The user should note that in some applications (where the lead resistance is not negligible) it is possible
that the selected voltage may be exceeded even when connected to a low resistance load. In this event,
if it is not possible to reduce the lead resistance in the current carrying leads, the user may wish to select
the higher clamp voltage after connecting to the test load and then re-select the lower clamp voltage
prior to the removal of the test load. This will ensure that the required voltage is not exceeded during
connection or disconnection, but will allow the correct value of the test load to be obtained.
For the 4165-1344 only, the 20mV clamp should be selected prior to reversing the polarity of the test
current.
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