A Single-Channel Printing Scaler for Photon Counting

Abstract

A device is described which counts pulses and generates serial code to punch a paper tape and produce formatted count listings on a Teletype. The digital counting mode employed by the printing scaler makes it ideal for photon counting or other event recording applications in spectroscopy. The count capacity is 5 digits (99 999 if decimal; 1 048 575 if hexadecimal). Provision is made to record initialization and overflow flags and two optional external flags. A data latch is included to allow simultaneous counting and printing for minimum dead time; the maximum print rate is 1 data point per sec on a 110 baud terminal. “Initialize” and “enable” signals must be supplied by external circuitry, such as a spectrometer timing and stepping control system. A “done” pulse is supplied by the printing scaler for use in external circuitry if desired. The circuit can also be used with other serial recording devices including an on-line computer; the baud rate is easily adjustable. This device contains 32 TTL SSI and MSI integrated circuits and a few associated discrete components. Our version was constructed on a single 36-position wire wrap breadboard with edge connector and housed in an inverted 8 by 12 by 3 in. chassis box with perforated cover. The required power can be obtained from an inexpensive 5 V, 1 A power supply.