The Gamma Counter LG-4 is designed for radioimmunoassay (RIA) and immunoradiometric assay (IRMA) in medium size laboratories employing isotope ¹²⁵I. The counter is an easy to operate instrument with no moving mechanical components enlarging his operation reliability.

The gamma counter carries out measurement up to 4 samples in 4 measuring channels. ¹²⁵I radiation is detected with NAI(Tl) well scintillators ensuring high detection efficiency of gamma radiation. Automatic gain control of photomultiplier tube for each measuring channel, based on light pulse from light emitting diode as reference, ensures high stability of the counter operation. Hardcopy of the calibration curve and of the measuring results is made on a band paper by a needle printer. Lead shielding around the radiation detectors and registration of the detector pulses in a window corresponding to ¹²⁵I energy range results in low background of natural radiation ensuring thus measurement of samples with low substance concentration.
The measurement is carried out under the control of a microprocessor software. Instructions at the counter display make calibration of the counter and the measurement of unknown samples easy. Two calibration curves are made during the calibration procedure: RIA (decreasing count rate) and IRMA (increasing count rate). The last calibration curve is stored in the counter memory and can be used later for another measurements.