Fluke 1595A - Manual (Page 73)

63
Making Measurements
Making A Zero-Power Measurement
c. Select the SETUP RS (F1) function key.
d. Select the DEFINE RESISTOR (F2) function key.
e. Select the ADD RESISTOR (F1) function key.
4. Enter a unique ID in the ID field. Pressing the ENTER key will open the Alpha-Numeric Interface for
text entry.
5. Enter the resistance value of the resistor in the RESISTANCE VALUE field.
Caution: The Resistance Value field is used in measurement for the calculation of the Rx resistance.
Entering this value incorrectly will cause measurement error.
6. Set the maximum measurement current allowed for the reference resistor.
7. If necessary, enter the calibration date and due date for the external reference resistor. The Super-
Thermometer will use the due date to warn the user when the resistor is due for calibration.
8. Select the SAVE (F1) function key to save the definition.
9. Press the EXIT key to go up one menu to the Set Up Rs screen. Use the Up/Down arrow keys to
highlight the Rs input to which the external resistor is connected.
10. Select the ASSIGN RESISTOR (F1) function key to open a list of defined reference resistors. Use the
Up/Down arrow keys to highlight the resistor’s definition. Press the ENTER key to assign the resistor to
the selected Rs input.
11. Now, when selecting the reference resistor in Section 7.2, Measuring a Temperature Probe, on page
61, step 6.a, the newly entered external resistor will appear as an option.
7.6 Making A Zero-Power Measurement
A temperature probe self-heats when measurement current is passed through its sensing element. Typically
self-heating will cause measurement error. The Super-Thermometer Zero-Power function allows the user to
measure how much a probe self-heats. It is also able to automatically measure a probe at zero-power. Use the
following instructions for performing a zero-power measurement:
1. Press and hold the EXIT key to go to the Measurement screen.
2. If necessary, suspend measurement by pressing the STOP MEASUREMENT (F1) function key.
3. Using the instructions in the Getting Started section, connect a temperature probe to one of the
measurement input channels.
4. Configure the probe definition ensuring that the MAXIMUM CURRENT field is set to a value equal to
or greater than 1.4142 times the nominal current value.
5. Open the ZERO-POWER MEASUREMENT screen by pressing the MENU key, then the MEASURE
MENU (F3) function key, followed by the ZERO-POWER MEASUREMENT (F5) function key.
6. In the Zero-Power Measurement screen, set CHANNEL to the channel where the probe is connected.
7. Set the SETTLE TIME field to a sufficient time period to allow the probe to self-heat and stabilize after
current is applied. For most probes 1 minute is sufficient.
8. Set the MEASURE TIME field to a time span that allows a sufficient number of samples to be taken.
For example, with a 2-second sample period and 2-second Display Interval, a 1-minute Measurement
Time will yield 30 samples.
9. If necessary, use REPEAT NOMINAL to set the Super-Thermometer to repeat nominal current
measurement after the 1.4142X step is complete. The difference between the beginning and ending
nominal current values will indicate if the probe was sufficiently equilibrated during zero-power
measurement.
10. When ready, press the START (F1) function key to start the zero-power sequence of measurements.
11. When the measurements are complete, the results are displayed on the screen.