The General Purpose Pulse Counting System is a self-contained instrument requiring only a mains supply and an external detector for operation. It is intended primarily for use in the nuclear industry where randomly occurring low amplitude pulses are counted. It is suitable for use with fission chambers and BF₃ and ³He detectors.

The instrument is housed in a 5U high, 19" rack mounting chassis. It is of modular in construction, being comprised of modules selected for particular customer requirements but typically includes: A Polarising Supply, Head Amplifier, Main Amplifier, Amplitude Discriminator, Scaler and Ratemeter.

Trips and Alarms can be incorporated and the Head Amplifier can be removed for remote operation.

EHT Unit PC/EHT1 Specifications:

The PC/EHT1 is a general purpose EHT unit with front panel switchable polarity whose output is variable by 10 turn potentiometer up to ±4kV. The output voltage is displayed by a 4 digit LED DVM. A facility is provided to rapidly discharge an external load.

Output Voltage (High)	400V to 4kV
Output Voltage (Low)	50V to 500V
Voltage Range Switch	Locking toggle
Voltage Control	Ten turn lockable
Output Current	0.5mA on 4kV range
Output Current	2.5mA on 500V range
Output Voltage Stability	100ppm/°C
Output Connector	SHV

Head Amplifier PC/HA1 Specifications:

The Head Amplifier is designed to amplify the current pulses from BF3 and Fission counters. It was specifically designed to be used with Cooknell Electronics General Purpose Counting System where it can be housed within the parent instrumentation or removed remotely to reduce the cable length between head and detector. However, because of its excellent interference immunity and breakdown protected input it can beneficially be used as an update for existing installed instrumentation systems. The signal input impedance is variable via a control on the main amplifier to accommodate different cable types. A 50 ohm test input is provided on the Head Amplifier to allow testing without disconnecting the detector. A 50 ohm monitor output is also provided for connection to an oscilloscope.

Input Connector	HN
Input Impedance	33 to 75 ohms
Signal Input Protection	4kV
Gain	2x104V/A ±10% into 50 ohms
Gain Temp-Co	200ppm/°C
Rise Time	8ns typ, 12ns max
Decay Time Constant	>3ms with current input
EHT Input Connector	SHV
Max EHT Voltage	±4kV
Test Pulse Input	BNC
Test Input Impedance	50 ohms
Test Input Gain	-14dB typ
Main Output Connector	TNC
Main Output Impedance	50 ohms
Maximum Output	±2.5V into 50 ohms
Monitor Output Connector	BNC
Monitor Output Impedance	50 ohms
Monitor Output Gain	As main output
Maximum Output	±0.3V into 50 ohms

Main Amplifier PC/MA1 Specifications:

The Main Amplifier is a switched gain switched bandpass design housed in a well screened enclosure. Control lines interconnecting the front panel mechanical switches and the internal solid state signal switches are well filtered on entering the enclosure to ensure interference immunity. The output signal can be inverted and a monitor socket provides a buffered output to aid diagnostics. A front panel Head Supplies socket is available to power a head amplifier and controls are provided to set the input impedance of head amplifier type PC/HA1.

Input Connector	TNC
Input Impedance	50 ohms
Gain	16dB to 69.5dB
Temperature Coef of Gain	200 ppm/°C max
Attenuator Coarse	0 to 48dB in 6dB steps
Attenuator Fine	0 to 5.5dB in 0.5dB steps
Time Constants	25, 50, 100, 200, 500 & 1500ns equal integrate and differentiate
Main Output Amplitude	±1.5V min into 100ohms
Monitor Output Impedance	50 ohms
Monitor Output Scaling	Main Output / 10
Monitor Output Amplitude	±0.15V min into 50 ohms

Amplitude Discriminator PC/DSC1 Specifications:

The Amplitude Discriminator compares an input signal with a positive settable bias voltage. The bias voltage is set on a lockable ten-turn control. When the input voltage passes through the bias voltage level this event produces a TTL compatible output pulse. A switchable Dead Time circuit ensures that another output pulse cannot be generated within the preset time. The bias voltage is displayed on a 3½ digit DPM.

Input Impedance	100 ohms
Discriminator Level	0.1 to 1.1V
Discriminator Stability	150uV/°C
Dead Time	50ns, 100ns, 300ns, 1us, 3us & 10us
Monitor Connector	BNC
Monitor Output	>1V into 50 ohms
Main Output	TTL

Scaler PC/SC1 Specifications:

The PC/SC1 scaler employs an 8 digit LED readout counter with manual Start / Stop controls together with a crystal controlled timebase to enable counting with gate times of 1, 10, 100, 1000 seconds and manual mode. An LED indicates when the gate is open and a second LED indicates an overflow condition. An audible 'tick' is available with the arrival of each pulse and a longer 'bleep' can sound the end of the selected counting period. A jack socket is available to drive a remote audio transducer.

Input	TTL from Discriminator
Counting Resolution	50ns
Gate Time	1, 10, 100 & 1000s
Timebase Accuracy	300ppm ±50ppm/°C
Ext. Speaker	3.5mm jack, 40-200 ohms

Ratemeter PC/RM1 Specifications:

The PC/RM1 linear ratemeter provides a horizontal moving coil edgemeter display of input PRF. Its full scale sensitivity is switchable in a 1, 2.5, 10 sequence from 1 to 10⁴ pps and the meter can be damped with a switch selectable smoothing control with time constants from 0.2 to 125 seconds. A reset push button enables the smoothing circuit to be rapidly discharged. A front panel DC output is available for an external meter/recorder. Overload input count rates in excess of 2x10⁷ will result in a beyond FSD reading.

Input	TTL from Discriminator
Ranges	1pps to 104pps
Output Connector	BNC
Output Amplitude	-10V FSD

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