Metal Samples MS2500L, Operator'S Manual

Page: 25 / 48

21
VI. Calibration Procedure
A. Disassembly
After unscrewing enclosure cover and disconnecting J5 connector, remove interconnected boards A1
and A2 from bracket.
Remove shield by removing nuts and washers from switches SW1 and SW2 and screws Z5 and Z6.
Replace both screws.
B. Equipment Needed
• 1 - Adjustable 18 Volt Power Supply
• 2 - Digital Volt Meters and Leads
• 1 - Frequency Counter and Probe
• 1 - Shorting Plug
• 1 - Spare Lead
C. Applying Power
Connect positive (+) lead of digital volt meter (DVM) to the positive terminal of J3/J6. Connect the
negative (-) lead to positive terminal of power supply. Attach spare lead to negative terminal of power
supply and other end to negative terminal of J3/J6.
Note: While making connections, power supply should be off. The power supply, DVM, and leads will
remain in place during all calibrations.
Turn power supply adjustment all the way down. Turn on power supply and DVM. Set volt meter to
read in the 200 milliamp range. (200.0 mA)
While watching DVM, slowly adjust power supply up to 18 Volts; making sure that the DVM reading
does not exceed 40.0 mA.
D. Frequency Calibration
Connect frequency counter ground to pin 8 on U12 and probe to pin 11 on U12.
Adjust R50 until the frequency read is 2730 Hz ± 1 Hz.
Disconnect frequency counter.