EM-M25 is an isolated True RMS converter designed for measuring AC voltage and converting the measured value into a standard 4–20 mA process signal. Available measuring ranges cover AC voltages up to 400 VAC.
True RMS measurement allows the module to measure both sinusoidal and non-sinusoidal signals. The measurement circuit and output circuit are galvanically isolated, and the output side obtains its operating power from the current loop.
The EM-M25 measures the effective RMS value of an AC voltage. Unlike simple average-responding converters, True RMS measurement can also be used with non-sinusoidal waveforms within the specified operating limits.
The supported measuring-frequency range is 45 Hz to 1 kHz.
The EM-M25 is available with measuring ranges up to 400 VAC. The source data identifies the following ranges:
The required range is selected according to the device wiring and configuration.
The measured AC voltage is converted into a 4–20 mA output signal. The output circuit is powered from a 12–32 VDC current loop, so no separate auxiliary supply is required.
With a 24 VDC loop supply, the specified loop resistance is up to 700 Ω.
The 4–20 mA output can also be converted into a 1–5 V signal by connecting a suitable resistor according to the connection diagram.
A 250 Ω conversion resistor produces a nominal voltage of 1 V at 4 mA and 5 V at 20 mA.
The signal scaling can be adjusted from −30% to +20%. This allows the output span to be matched more closely to the required measuring range.
The AC measuring circuit is galvanically isolated from the output-loop circuit. The specified isolation voltage is 1500 VAC.
The module includes protection against incorrect connections and voltage transients.
| Output-loop supply voltage | 12–32 VDC |
|---|---|
| Measurement principle | True RMS |
| AC measuring range 1 | 0–145 VAC |
| AC measuring range 2 | 0–230 VAC |
| AC measuring range 3 | 0–400 VAC |
| Current output | 4–20 mA |
| Optional voltage output | 1–5 V using a conversion resistor |
| Linearity error | < 2% with a sinusoidal input |
| Thermal drift | < 200 ppm/°C |
| Settling time | 0.3 s |
| Measuring-frequency range | 45–1000 Hz |
| Signal adjustment range | −30 … +20% |
| Isolation voltage | 1500 VAC |
| Maximum loop resistance | 700 Ω with a 24 VDC loop supply |
| Operating ambient temperature | 0 … +60 °C |
Ordering larger quantities +100pcs.
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