Please Note: the prices shown include delivery to mainland UK addresses only. Overseas buyers are very welcome but please read the important notes at the bottom of the page.

Also Available In Black

We have acquired a very limited number of high-quality Geiger Counters/scintillation meters, made by the highly respected British company, Mini Instruments. They were recently decommissioned by the UK's Atomic Weapons Establishment (AWE) and originally they were supplied with scintillation type probes. However, at some point the AWE modified these instruments so that they could be used with a much wider range of radiation probes, and powered by an external low-voltage AC supply.

These units have been thoroughly refurbished. This included testing of the high voltage counter and display circuitry and the cases have been given an extensive makeover. There's a choice of finish, traditional hammered black and yellow, we can even supply custom colours, details on request -- see below. We have also upgraded the external variable HT supply adjustment (approx 400 - 1300 volts), making it more accessible and easier to use and the obsolete PTE 100 probe connector, fitted by the AWE, has been replaced with a modern TNC type socket. They now have an internal battery holder (8 x AA cells) for fully portable operation and the AWE's low-voltage AC module has been removed and replaced with a standard DC connector socket for a 12 - 18 volt DC mains adaptor. They have been fitted with a standard 3.5mm audio jack, for connection to head or earphones, or to link to a PC, for data logging. Finally, the LED indicator for the AWE power adaptor has been re-purposed as an event 'flasher'.

The 5.40 is a classic design, characterised by the super tough metal case and the large and easy to read analogue meter. It has a logarithmic scale, showing from 0 to 2000 counts per second (cps). Meters like these are still used on modern Mini Instruments models for the simple reason that they maintain a high degree of accuracy and do away with the need for a range switch. It also has a built in sounder, with a mute switch and a battery check function.

We are offering these instruments with a choice of three types of probe. Alternatively you can buy one without a probe and tailor it to your own particular needs. Make your selection on the drop-down menu above the Add To Cart button. The basic options are:

  • Sensitive Pancake type probe, with a mica windowed GM tube,
  • All-metal probe, adapted from the classic US Civil Defense CDV-700 'hot dog' design. This is fitted with a sensitive thin-wall Geiger tube and a rotating shield, to discriminate between beta and gamma radiation (very limited quantity available).
  • A slim, rugged general purpose plastic cased probe, also fitted with a thin-walled beta/gamma sensitive Geiger tube.

Whichever type of probe you select the 5.40 will be set to the correct voltage before dispatch. It will also be pulse-calibrated to ensure as accurate a reading as possible on the meter display.

If you decide to order one without a probe, the variable HT output means that it can be used with a variety of different probe types iincluding ones using the most popular European, Russian and Chinese Geiger tubes, higher voltage US-made tubes and, of course, many types of scintillation probe requiring drive voltages up to 1.3kV. We can pre-set the required probe supply voltage on request and for more experienced users the manual includes instructions for DIY adjustment. We can also supply custom coiled connection cables (various lengths available) fitted with a TNC connector at one end and a connector of your choice (most common types) on the other end -- details on request. If you have any questions, just ask: meanwhile here's a few numbers:

Basic Specs - main unit

Probe supply voltage:             Variable, 350 volts to 1.3kV (preset according to probe)

Meter Display:                          Logarithmic scale, 0 - 2000 counts per second (CPS)

Audio:                                       Internal speaker, switchable mute, 3.5mm audio output jack

Visual Display:                         LED 'event' flasher

Power Requirements.              8 x 1.5-volt AA cells or external 12 - 18 volts DC (std 2.1mm DC connector socket)

Battery Life:                              Typically >300 hours (4-6 hours use per day)

Dimensions:                             165 x 115 x 155mm

Weight:                                      1.5kg (ex probe & batteries)

Supplied Accessories:             operating manual,  extendable connecting cable -- approx 1 metre (only with units purchased with probes)


Basic Specs B/SBT-11 Probe

Detector:                                     Mica window pancake type GM tube

Sensitivities:                               Beta, Gamma (limited Alpha sensitivity)

Beta Sensitivity:                         >0.156MeV

Operating voltage:                     280 - 350 volts

Probe Dimensions:                    160 x 35/62mm

Probe Weight:                             200g

Probe Connection                       TNC


Basic Specs C/SBM-20 Probe

Detector:                                     Thin Wall type GM tube

Sensitivities:                               Beta, Gamma

Operating voltage:                     350 - 475 volts

Probe Dimensions:                    142 x 24mm

Probe Weight:                             233g

Probe Connection                      TNC


Basic Specs P/SBM-20 Probe

Detector:                                     Thin Wall type GM tube

Sensitivities:                               Beta, Gamma

Operating voltage:                     350 - 475 volts

Probe Dimensions:                    180 x 25mm

Probe Weight:                             48g

Probe Connection                      TNC

Colour Choice

Please let us know if you have a colour preference. The options are Yellow or Hammered Black, or if you have any special requirements (this costs extra and may take longer). You can put a note on the order form or send us an email using the Contact Us link at the bottom of this page page.  

Some Important Stuff: As usual, whilst these units are fully operational Geiger counters, sensitive enough to detect low levels of normal background radioactivity up to and beyond scarily high levels, they are supplied on the understanding that they are for educational, experimental and consumer use and not recommended (or intended to be used) for serious scientific measurement, or any health and safety applications.

More Important Stuff: these units were manufactured in the 1980's; the internal circuitry and metal cases are as tough as old boots and in good but used condition. Externally there may be minor blemishes and small scratches on the housing and meter face - nothing serious, promise - and some examples may have some small holes on the back panel, used for the (now removed) AWE power supply modification. We will always endeavour to send you the best one that we have in stock but stocks are strictly limited so it's first come, first served. If you want one, do not delay!

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.

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Mini Instruments Type 5.40 (Refurbished) Geiger Counter/Scintillation Meter - NEW LOW PRICE

  • Product Code: Mini Instruments 5.40 (Refurbished) Geiger Counter
  • Availability: In Stock
  • £250.00

Available Options