Tormach PCNC 770 - Using Digital Multimeter for Electrical Tests; Measuring DC Voltage; Measuring AC Voltage; Measuring Resistance

Chapter 10
176
UM10350_PCNC770_Manual_0916A
Troubleshooting
10.2.4 Using Digital Multimeter for Electrical Tests
Almost all digital mulmeters have the capability of measuring AC volts, DC volts, and resistance.
These are the important funcons used when troubleshoong a PCNC mill. Two test leads are
required to measure these three funcons. While many meters have more than two receptacles in
which to plug leads, for our purposes the leads will always remain in the same two receptacles. One
receptacle is almost universally labeled COM (for common) and the black lead is to be plugged into
this receptacle. The other lead, most oen red in color, is plugged into the receptacle labeled VΩ
(for volts and ohms).
10.2.4.1 Measuring DC Voltage
Select the DC voltage scale on the meter. The scale may be labeled DCV or with the symbol:
DC voltage has polarity, so if the common lead on the meter is not placed on the common signal, the
voltage reads as a negave number. This does not harm the meter, but could be confusing in certain
cases. We strive to dene the common terminal when asking you to take a measurement.
10.2.4.2 Measuring AC Voltage
Select the AC voltage scale on the meter. The scale may be labeled ACV or with the symbol:
There is no polarity to AC voltage so either lead can be placed on either locaon being measured.
10.2.4.3 Measuring Resistance
Ohms are the units in which resistance is measured.
Select the resistance scale on the meter, most oen labeled Ω. There is no polarity to resistance
so either lead can be placed on either locaon we are having you measure; however, resistance
measurements are always taken with power o.
NOTE: When making resistance measurements on motors and other devices with low resistance, always
take a tare, or zero, reading on the meter before doing the resistance measurement on the motor or
device. A tare reading is a reading using only the instrument. In the case of using a digital mulmeter to
measure resistance, touch the probes together to get the tare reading. Subtract the tare reading from the
meter reading when measuring the resistance of the motor to get a true value.
10.2.5 Contacting Technical Support
Always try to resolve any issue by rst reviewing this chapter (Troubleshoong). If this eort does
not produce results – and you do need to contact Tormach Technical Support – please review the list
below prior to calling. This will make the problem resoluon process go smoother.
1. Record mill serial number and have it available.