TM 10-6630-237-13&P
6.1
Expanded Millivolt Calibration. It is important to understand that in the expanded mode, the full scale will
span a range of 140 millivolts. Before deciding to use the expanded mode, the user must first establish that the total
millivolt range required will not exceed this value.
a.
Turn selection switch to mV (millivolt).
b.
Place probe in a solution of known potential.
c.
Use SET knob to adjust meter needle to read zero millivolts.
d.
Switch toggle switch from NORM to EXP (Expanded).
e.
Use SET knob to reset meter needle to the appropriate position for the millivolt range required.
f.
The meter is now calibrated in the expanded millivolt mode and will reflect a change of 140 millivolts
full scale.
g.
Before switching the meter back to the NORM (normal) mode, make certain to reset the meter needle
to zero millivolts. This prevents pegging the needle.
Example
For example, an oxidation-reduction potential (ORP) titration is to be performed, the starting solution
has an initial ORP of +200 mV and a final end point of +320 mV. The probe is placed in the starting
solution for the expanded mode calibration. Once in the expanded mode, the meter needle is set to -
600 millivolts. Therefore, in the expanded mode, the scale would read as follows:
-700 mV is now equal to 190 mV
-600 mV is now equal to 200 mV
-400 mV is now equal to 220 mV
0 mV is now equal to 260 mV
+400 mV is now equal to 300 mV
+600 mV is now equal to 320 mV
+700 mV is now equal to 330 mV
6.2
Expanded pH Calibration. It is important to understand that in the expanded mode, the full scale will span a
range of 1.4 pH units. Before deciding to use the expanded mode, the user must first establish that the total pH range
required will not exceed this value.
a.
Turn selection switch to pH.
b.
Calibrate the meter in the standard pH mode. (Section 6.0).
c.
Place probe in a standard buffer or a solution of known pH d. Use the SET knob to adjust the. Meter
needle to read pH 7.00.
e.
Switch toggle switch from NORM to EXP (expanded).
f.
Use SET knob to reset meter needle to the appropriate position for pH range required.
g.
The meter is now calibrated in the expanded pH mode and will reflect a change of 1.4 pH units full
scale.
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