Electrical Tachometers

Speedograph Richfield

Synonymous with Quality Speed Products.


The electronic tachometer system is based upon the principle of sensing rotational or peripheral speed by means of any pulse producing transducer, eg. A magnetic perception head, phototransistor, alternator or proximity switch.

Primarily designed to operate with magnetic perception heads, ferrous objects passing in close proximity of the perception head pole piece, varies the reluctance of the self-contained magnetic circuit and generate a train of

pulses, proportional to the to the rotational speed.

The signal from the perception head is transmitted by standard twin screened cable to the indicator.

The indicators are energised by either A.C. or D.C. supply, can be connected in parallel to give multiple indication for a single perception head, or one indicator can be used to display the output from a series of perception heads selected via a suitable low resistance switch (not supplied).

The moving coil assembly used in the M and F series electrical tachometers is mounted on a robust, jewelled suspension capable of withstanding shock of up to 30 g.

The full range of tachometers are temperature compensated, stabilised during manufacture and are capable of operating over an ambient temperature range of – 20 to + 70 degrees Celsius.

Typical system accuracies of  +/- 2% of full-scale deflection are achieved in industrial applications.

The number of variations possible within the MMC series of tachometers is extensive so we should be able to meet your needs from our ‘preferred’ range.

The preferred range has been selected in terms of size, presentation and other parameters to suit the majority of industrial applications.

The purpose of this range is to simplify selection and ordering procedures, thereby avoiding cost penalties and extended delivery times.

Please note any enquiry falling outside our preferred range would be subject to minimum quantities, increased price and extended delivery.


Scales:                                           0-10, 0-15, 0-20, 0-25, 0-30, 0-40, 0-50, 0-60, 0-80

Multiplying Factor:                        x1, x10, x100, x1000

Legend:                                         RPM, MPH, km/h, UNITS / MIN, INS / MIN,  METRES / MIN.                                  

Pointer rotation:                             Clockwise  Centre zero (D.C. only)

Illumination:                                   Light slots provided for back-panel illumination

Window:                                         Glass

Accuracy:                                      +/- 2% full scale deflection between 5 – 100% of    full scale. 

Transducer:                                   EMP perception head or similar pulse producing  device

Supply:                                           10 or 20 Volts r.m.s.

                                                         11.5 – 16 Volts D.C.

                                                         19 – 31 Volts D.C.

                                                         100 mA max.

Termination:                                 Screw terminals at rear of instrument

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Speedograph Richfield Automotive division

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