Wahl ST2200 User Manual page 23

ST2200 Soldering Iron Tester User Manual
7.13 Millivolt Calibration AC ONLY- See Figure 7.
7.13.1 Connect the Millivolt source, True RMS Millivolt meter (AC reference voltmeter)
to ST2200 as shown in Figure 7. For best results, solder a small piece of wire to
the solder bead of the tip sensor and attach the alligator clip from the AC Millivolt
source to it.
7.13.2 Set the AC millivolt source to 50 or 60 Hz, depending on your local line
frequency. The source should be synchronized to the line frequency for best
results. Failure to do so may result in an unstable display for Millivolt readings.
7.13.3 Set Function Selector Switch to MILLIVOLTS AC ONLY and Input Selector
Switch to TIP TEST positions.
7.13.4 With the Millivolt Source power switch set to OFF, note the AC reference
voltmeter reading (call this V1) and adjust R19 for an ST2200 display reading of
0.02mV. NOTE: In the event that the unit is at 0.00mV and fluctuates negative
by as little as .01mV the FAIL MV/OHM indicator will flash Red, thus indicating
a false failure. To prevent this, an offset bias of .02mV is adjusted in during
calibration.
7.13.5 Turn the Millivolt Source power switch ON and adjust it's output to 20.00mV
RMS plus V1 reading from step 7.13.4. The AC reference voltmeter should
indicate 20.00mV + V1.
7.13.6 Adjust R16 for a display of 20.00 mV RMS on the ST2200.
7.13.7 Turn the AC Millivolt Source power switch to OFF and touch up R19 as needed
for a 0.02 display reading on the ST2200. Repeat Steps 7.13.4 through 7.13.6 as
necessary for the best calibration.
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