Temperature Measurements; Using A Transistor As A Temperature-Sensing Device - Tektronix 7D12 Operator's Instruction Manual

4. Select the desired full·scale voltage range by setting
the MODE/RANGE control to one of the four DC VOLTS
ranges with the gray front-panel background.
5. Connect a compatible probe such as the P6058 to the
M 1 PROBE connector.
When connecting the probe to the PROBE connector,
the two connectors must be correctly aligned. Dam-
age to the terminals can result from forcing the
connector and jack together. Refer to the probe
instruction manual.
6. Apply the voltage to be measured between the probe
tip and the common strap on the probe. Do not use the
COM INPUT connector when making a measurement with
the probe.
7. The readout will display a "+" preceding the voltage
read ing if the probe tip is positive with respect to the
common strap, and "-" if the probe tip is negative with
respect to the common strap.
Voltage measurements with the probe are essentially the
same as with test leads. The probe is a straight-through
device; i.e., it provides no attenuation to extend the
measurement range. The probe is shielded to minimize
pickup of electrostatic interference. (For more information,
see the instruction manual for the probe.)
Temperature Measurements
The M 1, in conjunction with a temperature sensing
probe such as the P6058, can measure temperatures from
-55°C to +150°C in one range. (See Ml Options in Section
5).
To measure temperature, use the following procedure:
1. I nsert the M 1 Module into the 7 D 12 A/D Converter
and install in any available plug-in compartment of a
7000-series oscilloscope.
2. Turn the oscilloscope power on and allow twenty
minutes warmup.
®
Ml Operating Instructions-7D12 Operators
3. Advance the oscilloscope Readout control to obtain a
usable readout display (if necessary, refer to the oscillo-
scope instruction manual).
4. Connect the temperature-sensing probe to the front-
panel PROBE connector.
When connecting the temperature probe to the
PROBE connector, the two connectors must be
correctly aligned. Damage to the terminals can result
from forcing the connector and jack together. Refer
to the probe instruction manual.
5. Set the MODE/RANGE switch to TEMPERATURE.
6. Apply the probe sensor tip to the device being
measured. For optimum temperature transfer, the surface
of the device being measured should be coated with silicon
grease and the probe tip should be applied squarely to the
surface.
7. Allow a sufficient amount of time for the probe tip
to "settle" before taking a reading. The time required
depends upon several factors. Generally, when the tip is
first applied to the device-under-test, the readings will
change rapidly. As the probe tip temperature approaches
the temperature of the device-under-test, the reading will
stabilize or "settle".
Using a Transistor as a Temperature-Sensing Device
Certain NPN transistors such as a 2N2484 can be used as
a separate sensor in place of the probe tip with little or no
selection of the device.
Typical accuracy, without recalibration of the M 1, can
be expected to be within 1°C for measurements from
-55°C to +125°C. However, device parameters could vary,
causing inaccuracies in the temperature readout as great as
±5°C.
If the measurement to be made requires an accuracy
greater than ±5°C, the calibration should be checked.
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