3. Place the temperature range switch in the desired position. Use the lower range, when
possible, for best resolution and accuracy. Power is automatically turned on when the range
is selected.
4. Place the probe tip on or in the material to be measured.
WARNING
Do not subject the probe to a voltage more than 30V
RMS, 42V peak above earth ground, or a shock
hazard may result.
5. Take the reading from the display. The reading is in °F (Model 868) or °C (Model
869). A leading minus sign indicates a negative temperature reading. An over range
a "1" followed by blanked digits) may indicate the need to switch to a higher range,
or show that the temperature is outside the measuring range of the instrument, or
that the probe is open.
6. When the measurement is complete, place the on-off/range switch in the OFF posi-
tion to conserve the battery.
ACCURACY CONSIDERATION
Model 868 basic accuracy is specified as on page 1. Similarly, Model 869 basic
accuracy is also specified on page 1. Keep in mind that these accuracy figures are for
4-wire probe operation with a lead resistance of less than 50 (each lead). Thus,
4-wire probes should be used, whenever possible, to maintain the highest accuracy.
Accurate readings can also be made with the instrument in the 3-wire mode with a suit-
able 3-wire probe. For best accuracy, however, lead resistance should be no more than
10per lead. Also, readings made in the 3-wire mode are sensitive to variations caused
by changes in lead resistance as well as to differences in lead resistance. For example,
a difference of only 38m(0.038) in lead resistance will cause a change of 0.1 °C
around 0°C. Four-wire readings are not affected by these lead resistance variations.
Accuracy figures do not include possible probe errors, which could affect overall mea-
surement accuracy. Probe errors near 32°F for the Model 868, and near 0°C for the
Model 869, can be minimized by recalibrating the instrument for use with a specific
probe. For probe calibration procedures, refer to the calibration section of this manual.
