Unlike other NCV detectors with only one sensitivity
level—and therefore the ability to detect only one range
of voltages (typically 50 to 600VAC)—General’s VR40 has
four sensitivity levels. They were chosen to optimize
voltage detection over four practical ranges: 12 to 25VAC,
70 to 125VAC, 150 to 240VAC and 250 to 600VAC.
The ability to detect the presence of 12VAC in non-
contact fashion comes in very handy during
troubleshooting of branch circuits and process plant
and industrial automation systems and equipment such
as gas and water valves, fans, lights, relays, inverters,
solenoids and horns. 12VAC is also commonly used to
power hardwired commercial and residential building
doorbells/buzzers and thermostats. Separately, the
VR40’s ability to detect 480V using its lowest sensitivity
range makes troubleshooting and installing generators
and fluorescent lighting ballasts easier, faster and safer.
User-adjustable sensitivity does more than make the
VR40 more versatile. It also improves the instrument’s
performance. The value of the VR40’s highest sensitivity
level (12 to 25VAC) is obvious: it allows non-contact
detection of 12VAC, an ability that most other NCV
detectors lack. However, the VR40’s lower sensitivity
levels, which cover common AC power voltages, also
have great value, for the following reason.
4
