UK Shipping included; overseas buyers see important note at the bottom of the page**

Here's a very rare opportunity to own a classic vintage British-made Geiger counter. The Mini Instruments models 5.10 and 5.40 have been a popular choice in education, industry and research for several decades and we have a small stock of fully refurbished instruments ready for dispatch.

Although they have been around for a few years**** they have proved to be extremely robust and reliable and continue to work as well as they did when they were made and compare favourably with, and even exceed the performance, durability, refinement and ease of use of many modern instruments.

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                                        First time buyer?  Please Click HERE

WE ALSO BUY SERVICE, REPAIR & CALIBRATE MINI MONITORS

                                           TO CONTACT US PLEASE SEE BELOW FOR MORE INFO

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The key feature, still used on current Mini-Monitor 900s, is the 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’…). 

*NEW! 9-VOLT OPERATION

Our stocks of Mini Instruments Series 500 Geiger Counters have now been upgraded to 9-volt operation. The circuits were originally designed to run on a 12-18 volt supply, which is fine, except that you need a lot of batteries, twelve AA cells to be exact. Not any more, the boffins at anythingradioactive have come up with a rather neat solution, a microchip-controlled power supply module, that uses  a single 9 volt PP3 type battery, OR a single 6 x AA cell battery pack.

As an added bonus we've designed a custom 3D-printed battery holder for both types. And in case you were wondering battery life is hardly affected. An ordinary PP3 lasts for several days of continuous operation and a 6 x AA pack can keep it going for a week or more. (N.B. Battery unning times are approximate, and your mileage may vary, dependent on battery type, probe and useage). 

And in case there are any collectors or purists out there, we've held back a small number of fully original, unmolested 5.10 and 5.40 ratemeters. Sorry, no more original probes for the moment, but if you have any special requirements  we may be able to help. Either way just ask and we'll do our best.

KEY FEATURES)

• NEW!* 9-Volt Upgrade on all models
• Detachable probe
  
• Adjustable HV supply (approx 350 - 700 volts & 450 - 1300 volts depending on model)
• Internal speaker (with mute switch)
• 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 dispatch
• Operating Manual (generic) with calibration info and circuit diagram included
• Six month no-quibble warranty
• Optional LED 'flasher' and DC supply socket POA

MORE GEEKY INFO

As far as performance, reliability and ease of use are concerned the two models are almost identical (Type 5.10 cases may have rounded or square corners). The only significant differences are that the Type 5.10's probe supply is adjustable from around 250 to 750 volts whilst the 5.40 goes from 330 to 1500-plus volts. Additionally, 5.40 models have a handful of extra components that make them suitable for use with scintillation type probes.  The result is two highly versatile instruments capable of using a wide range of probes and suitable for a variety of specialist and non-specialist applications. (The operating manual includes full details of how to carry out HV adjustments).

Refurbishment begins with a complete strip down. Where necessary cases are taken back to bare metal, primed and re-sprayed using top quality primer and paint to give them a fresh new look. (Custom colours and finishes on request,for details use Contact Us at the bottom of the page). 

All instruments are fully portable and self-contained, powered by internal batteries either  6 x AA cells or one 9-volt PP3 type battery. Some models also have external supply sockets so they can be used as bench instruments using a mains adaptor (12 - 18 volts DC, not supplied). Instruments without captive probe leads have TNC or PET connectors fitted (case and/or cable), making it a simple matter to exchange probes. An LED indicator/event 'flasher' and audio output socket is also available as an optional extra, ask for details. The output socket means it can be used with headphones, connected to an amplifier, or a PC, for data logging or analysis.

Prior to shipping every instrument is tested (not a single failure or return so far!), the HV is adjusted and the unit pulse-calibrated, according to manufacturer's protocols. A Calibration Check Certificate is provided.

CURRENT STOCK

9-VOLT OPERATION  

5.10 STS-5 (91991) 
£440.00 inc. UK Shipping

           
Probe Type:                                 SBM-20 thin wall GM tube rotating beta shield
HT voltage:                                 Variable approx 350 to 700 volts
Sensitivities:                                Beta, Gamma & X-Ray
Meter Scale:                                0 - 500 cps
Applications:                              detection, monitoring, contamination control
Power Requirements.                6x 1.5-volt AA cells or 9-volt PP3 battery
Condition:                                     A

9-VOLT OPERATION  

5.40 SBM 20 (5090) 
£470.00 inc. UK Shipping

             
Probe Type:                                 SBM-20 thin wall GM tube rotating beta shield
HT voltage:                                 Variable approx 450 to 1300 volts
Sensitivities:                                Beta, Gamma & X-Ray
Meter Scale:                                0 - 2k cps
Applications:                              detection, monitoring, contamination control
Power Requirements.                6x 1.5-volt AA cells or 9-volt PP3 battery
Condition:                                     A

9-VOLT OPERATION

5.40 44A  Scintillation Probe 5010
SOLD OUT MORE SOON

Probe Type:                                Scitillation: Mini Instruments Type 44A Nal (TI) crystal
HT voltage:                                 Variable approx 450 - 1500 volts
Sensitivities:                                Gamma & X-Ray
Meter Scale:                                0 - 2k cps
Applications:                              detection, monitoring, contamination control
Power Options                           6x 1.5-volt AA cells or 9-volt PP3 battery or AC adaptor
Condition:                                     A

** Very Important Stuff For Overseas Buyers:

The prices shown are for UK buyers and inclusive of delivery to mainland UK addresses. Non-UK shipping costs - PLEASE CONTACT US FOR AN UP TO DATE SHIPPING COST AS PRICES ARE CONSTANTLY CHANGING...

*** 5.40 'bare bones' models are not supplied with probes. The very wide range of HT voltage adjustment (between 450 and 1300 volts) makes them compatible with most probes types, up to and including Scintillation detectors. For added convenience on some models the voltage adjustment pre-set is mounted on the outside of the case. Original probes are in very short supply but its always worth asking using Contact Us at the bottom of the page.

**** Please note that unrestored units may have been in service for several years so there might 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.