TRANSDUCER FOR FREQUENCY MEASUREMENT |
The transducer converts the input frequency into a load independent DC current or voltage signal which may be used to drive a number of remotely installed instruments. The unique design of this transducer, which avoids the use of monostable multivibrators, ensures that good accuracy is maintained when measuring the frequency of signals with high harmonic content.
The output is protected against over voltage due to surges or accidental contact with insulation testers or the mains supply.
The incoming frequency signal is transformed in (1) and fed to capacitor circuit (2). The measuring method is according to the capacitor charge/discharge principle, i.e. the charging current of the capacitor is proportional to the frequency. The compensating current for the suppression of the lower frequency range (zero shift) is generated electronically. The difference of the charging and compensating current is fed to the output amplifier(3) which provides either a load independent current signal (with maximum burden) or a load independent voltage signal (with minimum burden). The auxiliary voltage is transformed in (4), rectified and smoothed in (5) and is used to power the output amplifier and to provide the offset voltage for live zero versions. The auxiliary voltage may be internally bridged to the measuring voltage for mains frequency transducers.
| 1.Input | |
| Input quantity Un: | 10-600V AC |
| Input tolerance: | 10-120% of specified value |
| Frequency ranges: |
48-52Hz 45-55Hz 40-60Hz 55-65Hz. (other values on request) |
| Burden: | 2.5mA maximum |
| Overload in terms of rated input: |
1.2Un indefinitely 2.0Un 10 seconds |
| 2.Output | |
| Characteristic: | A or C or D or F |
| Output quantity: | Impressed current signal (voltage signal available on request) |
| Standard values: | 1, 5, 20mA |
| Maximum load: | 5k, 2.5k, 750 Ohm |
| Maximum output voltage: | 32V DC |
| Maximum current output: |
1.25x rated (typical) 2.00x rated (maximum) |
| Ripple: | 0.5% standard |
| Response time: | 210ms standard |
| 3.Auxiliary Power Supply | |
| Voltage: | 110V, 220V 50Hz ±20% (other values and DC on request) |
| Burden: | 2.0VA at rated output |
| 4.Accuracy | |
| Error limit at rated conditions: | ±1% at 23°C |
| Linearity error: | 0.5% |
| Long term drift: | 0.25% |
| Temperature shift: | 400ppm/°C |
| Variation with auxiliary supply: | 0.05% for ±20% variation |
| 5.Protection | |
| Impulse test between isolated sets of terminals: | 5kV (0.5J, 1.2/50 wave. IEC standard) |
| Voltage withstand rating between isolated sets of terminals: | 4kV, 50Hz AC for 1 minute |
| Power voltage across output: | 220V 50Hz indefinitely |
| Surge across output terminals: |
5kV, 25J 1kV, 4J |
| 6.Physical Constraints | |
| Working temperature: | -25°C to 13°C to 33°C to 55°C |
| Storage temperature: | -55°C to 75°C (above dewpoint) |
| Relative humidity: | 80% |
| Variation due to external magnetic field(worst case): | 0.05% at 400A/m, 50Hz |
| Position: | Surface mounting in any position indoors. |
| 7.Enclosure | DIN A |