Speed measurement and switching instruments

February 2001 Maintenance, Test & Measurement, Calibration

The microprocessor-controlled converter and switching instruments of the Jaquet FT1600 series are designed for monitoring measured variables as a function of time, such as rotational speed, speed, clock rate etc which has been converted to a proportional frequency by suitable pulse transmitters. (Pulse transmitters with signal amplifiers, NAMUR sensors or proximity switches win npn transistor output can be used with the FT1600 equipment series).

A 12 V sensor supply, rated at 35 mA, is available. The frequency input is isolated. For cascading two or more instruments with one pulse transmitter, a pulse output (floating open collector) is available.

The frequency measurement and switching instruments in this series operate on the period measurement principle.

The application of this technique offers advantages such as accuracy class 0,5%, good reproducibility and very short response or reaction times.

All the instruments are available in 230 or 115 V a.c. and 18 to 33 V d.c. options.

Frequency/current converter FTW1613

This converter has a 4 to 20 mA output, proportional to the input frequency. It is controlled by corresponding DC measuring instruments such as meters, recorders, etc. Frequency/current converter FTW1613 can also be used as an actual value sensor for rotational speed control loops as it has a short response time of one period of the input frequency +5 ms.

The end-of-range frequency is set at the front using four coding switches. The setting range extends from 0 to 30 kHz with a minimum range of 0 to 0,999 Hz.

Frequency relay FTF1623

The frequency-relay is a rotational speed-dependent switching device. Via a floating changeover contact (250 V max 1 +, 50 W) it responds when a frequency has exceeded, or dropped below, a threshold.

The switching threshold can be set over the range 1 Hz to 30 kHz by means of four coding switches at the front, with a hysteresis of 1 or 5%.

A start-up bridging time can be set on an additional switch (range 1 s to 30 min in steps of 1:3). The normal/inverse switching function is programmable.

Speed monitor FTR1643

A rotational speed monitor serves for monitoring a setpoint speed or as a zero speed detector.

The parameters for the switching point are formed by a number of pulses (1 to 100) per time division (0,1 to 3600 s in steps of 1:3 to 1:6). These two values can be set on coding switches at the front. The switching point hysteresis may be 1 or 5%. The reaction time is one period of the input frequency + 5 ms.

The speed monitor FTR1643 also offers a facility for start-up bridging with an adjustable duration. The initial bridging time is started by applying the auxiliary power or via a terminal bridge.

The relay setting is indicated by an LED at the front.

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