Which model of laser tach should I use with my vbX instrument?

The information provided is for help with Commtest Instruments products:

vbSeries® (vbX) instruments

QUESTION

Which model of laser tachometer should I use with my vbX instrument? My older-model tachometer appears to be working correctly (pulse LED flashing and laser diode on), but I see no readings on my new vbX.

ANSWER

The laser tachometers that shipped with vbX instruments prior to serial number 40,800 do not work with newer instruments.

Instruments with serial numbers greater than 40,800 (equipped with a second USB port for flash drives) use a low voltage 5 Volt tachometer output and must use the low voltage MiniVLS211/N Ex rated laser (Commtest product code LASA0315).

Instruments with serial numbers lower than 40,800 (those with only a single USB port) output the full battery voltage of 6.5 - 8.4 Volts and should be used with the MiniVLS213 laser (Commtest product code LASA0062).

The two laser types:

laser_tach_IS

The MiniVLS213 laser tachometer that shipped with earlier instruments requires a minimum output of 6 Volts to operate correctly, and therefore will not work with newer instruments. The laser diode will activate and appear to work correctly, but the instrument will be unable to detect return pulses and no readings will be taken.

The new Ex rated low-voltage MiniVLS211/N laser tachometers will work with the older instruments, but will be over voltage. We therefore do not recommend this practice.

To comply with CSA Class I, Division 2 Hazardous Locations requirements, all instruments bearing the CSA logo MUST use the low voltage MiniVLS211/N laser tachometers.

FAQ ID: 19596 Last Reviewed: 30 July 2008