Model 6517B Electrometer Reference Manual Section 4: Basic measurements
6517B-901-01 Rev. C / August 2015 4-39
The effect on instrument performance can be considerable if enough of the unwanted signal is
present. The effects of EMI can be seen as an unusually large offset, or in the case of impulse
sources, erratic variations in the displayed reading.
The instrument and experiment should be kept as far away as possible from any EMI sources.
Additional shielding of the instrument, experiment, and test leads often reduces EMI to an acceptable
level. In extreme cases, a specially constructed screen room may be required to sufficiently attenuate
the troublesome signal.
External filtering of the input signal path may be required. In some cases, a simple one-pole filter may
be sufficient. In more difficult situations, multiple notch or band-stop filters, tuned to the offending
frequency range, may be required. Connecting multiple capacitors of widely different values in parallel
maintains a low impedance across a wide frequency range. Keep in mind, however, that such filtering
may have detrimental effects (such as increased response time) on the measurement.
Relative humidity and external temperature readings
With the appropriate equipment connected, the Model 6517B can measure relative humidity and
external temperature. Humidity and external temperature readings are provided as a multiple (NEXT)
display for each function. These readings can also be included as data elements for the bus
interfaces (GPIB and RS-232), and for the buffer.
Relative humidity
The Keithley Instruments Model 6517-RH option is used to measure relative humidity. This sensor
plugs into the connector label "HUMIDITY" on the rear panel of the Model 6517B. Note that an
extension cable (part number CA-129-1) is supplied for the humidity sensor.
Humidity measurements are controlled (enabled or disabled) from the A/D-CONTROLS
(DATA-STAMP) item of the GENERAL menu (see GENERAL for more information).
External temperature
The Keithley Instruments Model 6517-TP option is a "K" type thermocouple sensor that is used to
measure external temperature. This sensor plugs into the connector labeled "TEMP TYPE K" on the
rear panel of the Model 6517B.
External temperature readings are controlled (enabled or disabled) from the A/D-CONTROLS
(DATA-STAMP) item of the GENERAL menu. Measurement units (°C, °F or K) are selected from the
DISPLAY (TEMP-UNITS) item of the GENERAL menu (see GENERAL for more information).
Do not allow the exposed thermocouple sensor to come in contact with chassis ground or to a
voltage. This results in erroneous readings. The thermocouple must be electrically insulated before
attaching it to a device that is at chassis ground or has a voltage on it.
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