A device assembly having multichannel analyser capabilities and designed to detect and quantify radiation emissions and differentially identify unknown radioactive isotopes. Typically a component of imaging or laboratory systems, it has the capability to be adjusted in a manner that allows the user to simultaneously count and differentiate emissions from multiple radioactive isotopes. It incorporates a spectrometer, permanently attached or interchangeable detectors, e.g., probes, a linear amplifier, an adjustable pulse height selector, automated spectral analysis and processing capabilities, a printer, and a display (usually a scalar or count rate meter).