bPAD+ VR Single Channel Analyzer


The bPAD+VR is an enhanced version of the bPAD+ intelligent Single-Channel Analyzer. In this model, the analog output can be configured to deliver the pulse signal, as in the bPAD+, or a variable voltage level which is proportional to the discriminated count rate. This feature is useful, for example, in flow count rate instruments or HPLC systems.  
bPAD is a compact microcontroller-based Single Intelligent Channel Analyzer. The device contains a Preamplifier-Amplifier-Discriminator with TTL digital output. The bPAD also includes its own high voltage power supply for operating standard 14-pin photomultiplier tubes, which are commonly used with scintillator-type radiation detectors [e.g. PVC, NaI(Tl), LaBr, CeBr, etc].
The device is therefore useful as a compact system to monitor the count rate in an energy region of interest. The detected signal is output as a TTL pulse, making it compatible with most industrial, environmental and laboratory counting systems. In contrast with traditional SCAs the bPAD is fully controlled by a microprocessor, providing easy setup and “smart” modes of operations. bPAD parameters can be conveniently set via USB with a PC and the provided configuration software.


    • Compact Single Channel Analyzer with microprocessor control on a 14-pin photomultiplier tube base
    • Integrates Preamplifier-Amplifier-Discriminator and HV power supply
    • TTL output
    • USB communications
    • Device can be powered from USB and/or an external supply of 9 to 36 Volts via a pluggable terminal block
    • Compact size of 56mm (D) x 71mm (H)  - [2.2 in. (D) x 2.8 in. (H)]
    • Very low power consumption, 1 watt maximum.
    • Miniature and efficient high voltage power supply
    • Configuration software for easy setup and visualization of device operation, also implements a “pseudo-PHA” mode of operation
    • LED indicators for communication status and device power, HV power and incoming count rate (ICR)


The bPAD is an advanced, microprocessor-based, compact electronic device that integrates a charge sensitive preamplifier, a variable-gain amplifier and a window discriminator; all in a 14-pin photomultiplier tube base. This electronic device outputs a TTL pulse per photo-event detected by a scintillator detector in the energy range of interest. This type of device is also often referred to as a Single Channel Analyzer (SCA). bPAD also includes a miniature, programmable and efficient high-voltage supply to provide the power necessary to operate the most widespread range of photomultipliers used with scintillator detectors. The output voltage can be set in the range from 0 to 1500 Volts with a resolution of 4096 steps.
Since the bPAD is a microprocessor-controlled device, it benefits from being easy to setup. The device connects to a PC via its USB interface, and by using the provided software all the operational settings can be configured and fine-tuned for any kind of scintillator detector. Once the setup is complete, all the settings are saved into the device’s non-volatile memory. The PC software also comes with a “pseudo-PHA” acquisition mode. In this mode, the software slides the single-channel window over the whole input range, constructing in such a way an energy spectrum. By using this spectrum, the user can visually identify the energy range of interest and immediately set the boundaries of the bPAD discriminator window. This represents a large improvement over the traditional “blind” method used with most other SCAs.
bPAD has two modes of operation:
    • Integral: where counts are output for signals above a single energy threshold level
    • Differential: where counts are output for signals within a defined energy window (SCA)
The output pulses correspond to counted events in the energy window of interest. They are 5-volt TTL signals
with 2.5 µsec duration. The bPAD can be ordered to output pulses with a duration of 10 µsec instead.
The bPAD can be powered via the USB connection or by an external DC power supply of 6 to 36 volts. 
Three color LEDs are used for status indications: Red for detector high voltage, Yellow for incoming count rate (ICR) and Green for power and communication status.
The bPAD is a compact device with a size of 65 mm diameter by 71 mm high (60 mm not counting the TTL
output connector) . bPAD weights less than 80 grams.
All the above-mentioned features make the bPAD+ a very attractive component for industrial and automated applications involving photon detection and counting.

Technical Specifications

Device and Digital Settings
    • Acquisition modes: Integral and Differential
    • Coarse gain: x1, x2, x4, x8 (optionally also x16, x32, x64, x128)
    • Fine gain: x1...x2 in 4096 steps
    • Upper and Lower Level discriminator resolution: 2048 steps
    • Output: 5 Volts TTL signals of 2.5 µsec duration.
High Voltage Power Supply
    • Miniature HV power supply embedded into the device assembly
    • Voltage: 0 to 1 500 Volts in 4096 steps
Data Communication
    • USB 2.0, cable included
    • TTL output via SMA connector, cable included
    • Analog output signal range of 0 to 2V, 50 ohm impedance, cable included
    • USB connector: type mini B, used for PC communications or powering
    • Power connector: pluggable terminal block, 9 to 36 Volts, plug included
    • Power consumption: 1 watt maximum
    • Size: Height 71 mm, Diameter 56 mm
    • Weight: Approximately 80 grams
    • Red LED for detector high voltage
    • Yellow LED for incoming count rate (ICR)
    • Green LED for power and communication status
    • The device is supplied with WindowsTM PC software for setup and pseudo-PHA, the software can also display the CPS value for the defined SCA region
    • The device is CE compliant

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