Multitek M300 Digital Panel Meter
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The digital panel meter range, known as the M300 series is primarily designed for use in the power industry, but offers a wide range of both AC and DC input parameters. The applications are limitless.
Customer adjustment of both "ZERO" and "SPAN" is permissible via potentiometers, accessible from the rear of the product.
The meters are 3½ digit with a digit size of 14.2mm (0.56") high, 7 segment matched LEDs allowing viewing from a wide range of angles and distances.
Essentially there are 3 main product types :-
AC Volts, Amps, Millamps.
DC Volts, Amps, Millamps, Millivolts.
With the combination of a mA input the M300-AD1 and the M100 series Power Transducer, parameters such as kW, kVAR etc. can be measured and displayed.
|THEORY OF OPERATION
Both AC Voltage and Current circuits are average sensing RMS calibrated. The input signal is transformed to a low level of AC. The transformer secondary voltage is fed to a precision active rectifier, the resulting DC signal is presented to an analogue to digital converter. The A/D converter uses a dual - slope integration method of conversion. The resulting digital information is used to drive the LED display.
DC Voltage and Current inputs are fed into high stability ranging components. The ranging components reduce the input signal to a 2 Volt level. If the input is below 2 Volts an amplifier is employed to derive 2 Volts. The 2 Volt signal is then presented to the A/D converter which provides the digital information to drive the LED display.
A frequency to Voltage F/V converter is used to convert the input signal to a DC signal. The resulting DC signal is fed in to the A/D convertor and the same process as in the AC and DC circuit described above takes place.