Small-sized ohmmeters "OK" and "M-57".

Instruments for adjusting and controlling the PTA.Small-sized ohmmeters "OK" and "M-57" were produced from the beginning of 1936 and 1941. Small-sized Pocket Ohmmeter `` OK '' has been produced since 1936. The upgraded ohmmeter M-57 has been produced since 1941. The "OK" ohmmeter was designed like a tree, and this is not a glued film, but a factory production. The ohmmeter `` M-57 '' was produced for a long time as probably none of the devices, its release was completed only in the late 70s. On the author's site of Vitaly Brusnikin, such an ohmmeter is dated 1975. The ohmmeter can measure resistance values ​​ranging from 20 ohms to 2 kilo-ohms with an accuracy of + - 10%. The overall measurement limit for an ohmmeter is somewhat wider, from 0 to 5 Kilo-ohms, but outside these limits, the reading accuracy decreases to + - 20%. The ohmmeter is powered by one battery for a pocket flashlight of the KBS-L-0.5 type, and it is enough for more than one year of operation. The zero setting in the ohmmeter is in front and there is a blocker of the magneto-electric system at the back.