Model 461950 Version 2.0 March 2005

5

Meter and Sensor Operation

Meter Operation

Mount and wire the meter as previously described. The Model 461950 Panel Mount

Tachometer was designed to measure and display RPM in the following ranges:

Ranges

Resolution

Accuracy (of rdg)

5 – 999.9 rpm

0.1 rpm

1000 - 9999 rpm

1 rpm

10,000 - 99,990 rpm

10 rpm

±(0.05% + 1 digit)

Extech sensors generate pulses that are counted by the meter and converted to RPM. The

meter computes RPM values based on the number of pulses detected in a given period of

time and provides an RPM display on the 4 digit (9999 count) LED.

Operation of the Proximity Switch Model 491955

The Extech Proximity Switch Model 461955 connects directly to the tachometer's input

terminals and measures up to 36,000 RPM (600 Hz). Proximity switches detect magnetic

(ferrous) objects as they pass the sensor, sending a pulse, one for each pass, to the

meter. The pulse LED on the switch lights with each pass. The meter then calculates RPM

and updates the LED display.

Operation of the Photoelectric Sensor Model 461957

Extech Photoelectric Sensor Model 461957 connects directly to the tachometer's input

terminals and measures up to 6,000 RPM (100Hz). When the sensor is properly powered

(by the voltage on terminal 3 of the meter), the green power LED (on the sensor) will

switch on.

Photoelectric sensors generate a light beam that is interrupted by an object as it passes

through the beam. Each time the beam of light is interrupted a pulse is transmitted to the

meter and the red status LED on the sensor blinks. The meter then calculates and displays

the RPM based on the number of pulses received in a specific period of time.

The sensitivity adjustment screw on the sensor may have to be adjusted so that one pulse

is generated for each interruption of the light beam. If the red LED turns on less/more than

once for each interruption of the beam, adjust the sensitivity screw.