M-91 (Mikroampermetr) 1949
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Since 1949, the microampermeter M-91 has been manufactured by the Leningrad plant Vibrator. The device is made on the basis of the M-91 galvanometer and differ from it only by the measurement limits and the parameters of the measuring mechanism (the opposing moment of the stretch marks and possibly the winding frame data). The microammeter was produced on the limits of measurements: 0 - 1; 0 - 3; 0"“10; 0 - 30; 0-100 microns. Accuracy class 1.0. Operating temperature range from 10 to 350C. The change in the instrument readings from temperature drift away from normal (200С) does not exceed - / 0.5% of the upper limit of the scale by every 10 degrees. for a length of 100 mm. There was a version of the device different from that shown in the photo - it had the power of the illuminator bulb not through the plug connector in the upper end of the housing (not shown), but through the cord with the plug mounted directly to the power delivery switch on the front panel. The price of the device is 540 rubles (according to the price list of 1954).
Information from collection of Valery Khartchenko