Racal 1991 Frequency Counter
The Racal 1991 universal timer/counter offer a unique combination of superior performance and measurement capability in a compact package.
Racal Electronics was a multinational manufacturer and service provider in telecommunications, security, data communications, defence radar and avionics, marine and energy electronics, radio communications, and specialised electronics.
Although often referred to as a frequency counter, this piece of equipment is capable of many more functions and operations.
The dual microprocessor-based counters provide outstanding operational simplicity with exceptional versatility. The measurement functions, which include frequency, period, time interval, ratio, totalise, phase and peak amplitude benefit from full GPIB programming.
For applications where speed is vital, the resolution may be varied between 3 and 9 digits to provide optimum speed/resolution performance. In addition, the ability to
reduce resolution is a highly desirable feature when making measurements on noisy or unstable signals.
The 1991 offers a 9-digit display for the resolution required to make accurate measurements. The 1991’s other outstanding features include auto-triggering and attenuating, direct digital trigger entry, comprehensive external arming, time-interval delay, extensive math functions plus offsetting and normalisation capabilities.
The 1991 Frequency range from DC to 160MHz; Channel A sensitivity is 25 mV rms up to 100MHz, above 100MHz, it triggers on 50 mV rms to 160MHz; Channel B has same sensitivity as Channel A except that the frequency range is 10 Hz to 100 MHz.
In addition to the 1991 unit, I have a 1992 unit which is identical, but with addition of a third signal input capable of measuring frequencies up to 1.3GHz.
The maintenance guide for the Racal 1991 can be downloaded here , along with the schematics or visit the downloads page for more files.