The Fieldpiece Optical Laser Tachometer, model SRPM2, is a non-contact tachometer that measures revolutions per minute on any spinning surface. It is designed to measure RPM or total count (total number of revolutions) on air conditioning and heating system blower motors and fans. An RPM reading out of spec can tell you that your wiring may need attention or that a motor is not running at maximum efficiency. It works up to four feet away and includes reflective tape required for testing. Replacement reflective tape is available. (Model RREF16).

How Does It Work?
SRPM2 is a portable standalone digital, laser tachometer. Point the laser at a fan blade or motor shaft and the RPM shows up immediately on the LCD.

SRPM2 works by reading reflected light from the laser. Each time the reflection is interrupted, a count is taken. Place a small piece of the supplied reflective strips on the target to make sure the laser is being reflected directly back to the instrument.

1. Press and hold ON for 1 second to turn on SRPM2.
2. Press Mode to toggle between RPM (revolutions per minute) and total count (total amount of revolutions).
3. Press TEST once to turn on laser and start testing. Steadily aim meter so that laser hits the reflective strip.
4. Press TEST again to turn off laser and stop testing.
5. Press Mem after taking RPM readings to cycle through that set of reading's Max, Min, and Last. A new set begins each time you press TEST.
6. Quickly tap ON once to power down, or wait 25 seconds for auto-off.

Reflective strips
SRPM2 requires a reflection of its laser to work. Proper use of reflective strips is critical to get accurate readings. To sense the reflected light, the reflective strip must be big enough, you must aim the laser accurately enough, and you must be close enough. Typically a reflective square 0.5? on a side read at 4 feet or under works well. Make sure that light doesn't reflect from either the surface of the target (other than the reflective strip) or from the background or foreground. For example, the fan blades of a fan running in front of a reflective background could cause multiple counts per revolution, multiplying the actual RPM.

If you find your measurement unstable or a multiple of what you think it should be, you may be "seeing" extra reflections of the laser. The reflector strip is designed to reflect the laser light back to the instrument, irrespective of the incident angle of the light. Therefore, to minimize extra reflections from the target or fan blades, don't point the laser perpendicular to the reflective strip. This will help deflect unwanted reflections from fan blades or shaft away from the SRPM2 sensor (see diagram).

A screen in front of the target can cause problems by reflecting the laser light directly back to the laser, thus interfering with the laser light reflected from the reflector.

Only apply one small piece of a strip onto the surface your measuring. Do not place one on each blade of the fan. If you do, and there are three blades, your readings will be three times the correct reading. When working with a very reflective surface, try to find a place that isn't reflective (e.g. the shaft) and place the strip there. You may need to wrap matte (not glossy) tape around the shaft and place the reflective strip on the tape to eliminate unwanted reflections.

Features and Benefits
  • Measures RPM without contact
  • Range: 1.5 to 99,999 RPM
  • Laser pointer
  • Works to four feet
  • Memory for Min., Max., and Last Reading
  • Ergonomic shape for better grip and aim
  • Highly visible, blue ruggedized boot

What's Included
  • Optical Laser Tachometer - SRPM2
  • (1) 1.0? x 0.5? strip of reflective tape (enough for approximately (20 + tests)
  • Small Single Pocket Case - ANC2
  • (3) 1.5V(AAA) batteries (installed)
  • Operator's manual

For additional technical specifications, please see "Owner's Manual & Specifications" below.
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Manuals (2)
Laser Tachometer
1.5 rpm to 99999 rpm 0 to 99999 counts
(at 75ºF ambient) 0.1rpm 1count
Laser Power:
less than or equal to 2mW
Operating Temp Range:
-0.4ºF to 104ºF
Base Time:
25 seconds without use
13mm 5digits LCD
Suggested Distance from Target:
less than 40 inches when using 0.5? x 0.5? strip
Battery Type:
1.5V(AAA) x 3 (installed)
Battery Life:
35 hours (operating) 1 year (off)
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