Here's a rare opportunity to own a classic British-made Geiger counter. It has been a popular choice in education, industry and research for several decades and is now available for personal users. The two models featured are the Mini-Instruments type 5.10 and 5.40, designed and manufactured in the 1980s and 90s. Although they have been around for a few years they have proved to be extremely reliable and continue to work as well as they did when they were made. There is no reason to suppose why they shouldn't continue to do so for many years to come. They have been extensively refurbished and updated by anythingradioactive, to the point where they now compare very favourably, and even exceed the performance, durability, refinement and ease of use of many modern instruments.

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 The key feature, and still used on modern Mini-Instruments (now Thermo Scientific) products, is a large and very easy to read moving coil meter, with a clever logarithmic scale. In a nutshell this means there is no need for a range switch and it can accurately display (in counts per second or cps) both high and low level readings (from normal background, to ‘get the hell out of there’…). Other highlights include:
 

• Internal speaker (with mute switch)
  
• LED ‘event’ flasher
  
• Audio output socket
  
• DC supply socket
  
• Detachable probe
  
• Adjustable HV probe supply
  
• Battery Check function
  
• Sturdy, compact metal case with carry handle and probe cradle
  
• Convenient ‘curly’ probe cable lead
  
• Portable operation with long battery life
• Calibrated prior to despatch
• Free Mains Adaptor -- Limited Supply, First Come First Served! 
  
  

 
Technically, visually and as far as performance, reliability and ease of use are concerned the two models are almost identical. They were originally configured to use hard-wired detection probes but their readily adjustable high voltage (HV) circuitry means that they can be used with a very wide range of detection devices. This includes standard Geiger Müller (GM) tubes, 'pancake' type GM probes and even advanced Scintillation probes. The result is a highly versatile instrument, capable of functioning in a wide variety of specialist and non-specialist applications and environments (For advanced users the operating manual includes full details of how to carry out HV adjustments).
 
The refurbishment begins with a complete disassembly of the cases. They have been stripped back to bare metal and re-sprayed using top quality paint to bring them back to near showroom condition*. Incidentally, we can also apply custom colours and finishes - details on request.
 
Most of the Type 5.40 units that we have were originally supplied to the UK's Atomic Weapons Establishment  (AWE), which carried out a number of modifications. They included adapting the power supply for bench operation, adding an external HV output control (approx 350 - 1400 volts), and fitting a probe connector. Following decommissioning from the AWE we have either removed or adapted the mods. The 5.40 now operates as a fully portable instrument, powered an internal battery pack(s) requiring 8 standard 1.5 volt AA cells. It's still effective as a bench instrument as we’ve fitted a socket for a standard mains adaptor (supplied) and we’ve replaced the obsolete PTE 100 probe connector with a modern TNC connector. We’ve also re-purposed an LED indicator, (fitted by the AWE for the power supply modification), as an event 'flasher', and given it them an output socket (3.5mm jack), so they can be used with headphones, connected to an amplifier, or a PC, for data logging or analysis.
 
The type 5.10 units have also been extensively refurbished to the same standard, with TNC connectors, LED flashers, external power supply and audio sockets. The main differences between the two models are that the 5.10 retains the original internal HV adjustment mounted on the PC board), and the voltage range (250 - 700 volts) which covers most common types of GM detector. This can be extended on request to cover a similar range to the 5.40.  
 
After reassembly each unit is extensively tested (not a single failure so far!), adjusted and pulse-calibrated – the latter is re-checked immediately prior to shipping.
 
Currently we are offering these units with a choice of five types of probe (other types are available, or you can choose to your own probe, just ask...). Instruments with supplied probes are set to the correct output voltage. Please note that some probes are in very short supply, so order early. The standard offerings, which you can select from the check boxes when ordering are:

  
AR/ZP1A: factory-original 20mm dia. mica window GM tube in a new housing, sensitive to Beta, Gamma and high-energy Alpha radiation.
 
B/SBT-11: miniature mica-window flat pancake type Geiger Müller detector, sensitive to Beta, Gamma and high energy Alpha. 
 
C/SBM-20: thin-walled Geiger Müller tube, sensitive to low levels of Beta and Gamma radiation. Housing adapted from probe supplied with US made Civil Defence (CDV) instruments. Features rotating sleeve for discriminating between Beta and Gamma radiation.
 
P/SBM-20: thin-walled Geiger Müller tube, Beta & Gamma sensitivity, lightweight and rugged.

BASIC SPECIFICATION  

* Please note that these units have been in service for several years so there may be some slight marking (scuffs, small scratches, etc.) on the meter face. There may be other cosmetic blemishes, however these are generally minor in nature. 

Very Important Stuff For Overseas Buyers:

The prices shown are for UK buyers and inclusive of delivery to mainland UK addresses. Overseas buyers should contact us before ordering for shipping options, which vary according to location. Please also note that this item may be prohibited or restricted in some countries.