Frequency-Voltage/Current Transducer FVM 90
General Description
This measurement transducer converts an input frequency to a proportional output analog signal (current 0/4-20 mA, voltage 0-10 V). The power supply (24 V DC or AC), the input and the output stages are galvanically isolated from one another. The output value (0-20 mA, 4-20 mA, 0-10 V) and the measurement range (1, 1.4, 2.5, 3.333, 5, 10 kHz) are selected via DIL-switches. The zero point and range can be calibrated precisely via two potentiometers with an adjustable range of 5-10%.
Construction: DIN-Rail housing
Technical Data
| Frequency input (opto-coupler), square wave | |
|---|---|
| min. input voltage (high) | 3.5 V (worst case, incl. aging) |
| typical input voltage (high) | 2.8 V |
| max. input voltage (low) | 0.8 V |
| max. operating voltage | 13 V |
| max. over-voltage | 30 VDC |
| typical input impedance | 1 kOhm |
| min. impulse width | 20% Duty cycle (min. 5 µs/1 µs low/high) |
| input filter | ca. 100 kHz cut-off frequency |
| range | 1 kHz, 2.5 kHz, 3.33 kHz, 5 kHz, 10 kHz |
| error range switching | max. 0.5%, at 1 kHz 3% (with respect to FS) |
| analog output (voltage) | |
| typical output impedance | 75 Ohm |
| max. voltage | 10.5 V |
| max. current | 5 mA |
| min. voltage | 30 mV |
| max. switching error V <-> mA | 0.5% (with respect to FS) |
| analog output (current) | |
| max. burden | 350 Ohm |
| max. current, typical | 20.5 mA |
| min. current, typical | 5 µA |
| max. switching error 0 -> 4 mA | 2% (with respect to FS) |
| Time response, ripple | |
| typical cut-off frequency low pass | 2 Hz/5 Hz (1 kHz/10 kHz-range) |
| typical transient response time (to 1%) | 100 ms (10 kHz), 300 ms (1 kHz-range) |
| typical output ripple | 0.1% (with respect to FS) at 100 Hz |
| Transmission error | |
| max. linearity error | 0.05% (with respect to FS) |
| max. amplification drift | 70 ppm/K |
| change in supply voltage | no effect (int. stabilisation) |
| Voltage | |
| min. supply voltage, typical | 19 V DC or AC |
| max. supply voltage | 30 V DC or AC |
| current consumption, typical | 35 mA (with 20 mA load: 55 mA) |
| isolation test voltage | 750 V |
| Temperatures | |
| specified operation | 0/50°C (32/122°F) |
| operative | -20/70°C (-4/158°F) |
| storage temperature | -20/80°C (-4/176°F) |
Operating Instructions
Connections (screw terminals)
1: power supply + (24 V AC/DC)
2: power supply - (24 V AC/DC)
3: analog Out - (analog ground)
4: analog Out + (current 0/4-20 mA or voltage 0-10 V)
7: frequency In - (digital signal ground)
8: frequency In +
Programming Switches
The programming switches can be found inside the module on the rear of the printed circuit board. Carefully remove the plexiglass cover and remove the circuit board by gently pulling at the screw terminals.
| Range | Switch 1 | Switch 2 | Switch 3 |
|---|---|---|---|
| 1.0 kHz | off | off | off |
| 1.24 kHz | off | on | off |
| 1.416 kHz | on | on | off |
| 3.333 kHz | on | off | on |
| 2.5 kHz | off | off | on |
| 5.0 kHz | off | on | on |
| 10.0 kHz | on | on | on |
The measurement range can be increased or decreased by about 8% via switches 5 and 6. In this way the adjustment range of the potentiometer can be kept relatively small. A large adjustment range often results in long term drift.
| Measurement Range | Switch 5 | Switch 6 |
|---|---|---|
| +8% | off | off |
| -8% | on | on |
| 0% | off | on |
| Switch 4 | Switch 7 | Switch 8 | |
|---|---|---|---|
| 0-10 V | off | on | off |
| 0-20 mA | off | off | on |
| 4-20 mA | on | off | on |
Adjustment
The zero point is adjusted via the "Offs" potentiometer, and the end value adjusted via the "Gain" potentiometer. The zero point should be adjusted first and then the final value. For larger adjustments, this procedure may have to be repeated several times. For additional reliability, the output value should be measured at half the measurement range.
If the final value cannot be adjusted via the potentiometer, then switch 5 or 6 should be used to shift it.
An even more reliable zero point can be achieved by applying 2% of the maximum input signal (20 Hz, 50 Hz, 100 Hz, 200 Hz for 1 kHz, 2.5 kHz, 5 kHz, 10 kHz input range) with a subsequent adjustment ("Offs" potentiometer) of the output value (0.2 V at 10 V, 0.4 mA at 0-20 mA and 4.32 mA at 4-20 mA).