Mini Monitor 900 Series Geiger Counters and Ratemeters, designed and  manufactured in the UK by Mini Instruments Ltd (now owned by Thermo Electron/Scientific, also sold under Morgan & Fisher brand names) are amongst the most highly-respected radiation and monitoring instruments in use today.

Over the years Mini Monitor 900s have earned an excellent reputation for reliability, performance, versatility, ease of use and value for money. The 900 series continues to be a popular choice in education, research, medicine, industry and amongst environmentalists and enthusiasts. We stock a wide range of pre-owned instruments, all thoroughly tested, checked and the ratemeter calibrated* and where necessary, refurbished to a high standard. Here’s just a brief outline of the key features:
 

• Tested and Calibrated prior to dispatch*

• Large, logarithmic meter, accurately displays both very low and high levels 

• Portable & bench operation using 6 x AA cells or optional mains adaptor -- see important note below. Factory-built mains-only variants also available for most models. See listings or ask for details 

• Battery life 300 hrs (typical, 4 hrs use per day)

• Ease of use – single control for battery check, power on & mute

• User-settable threshold alarm

• Battery check

• Built-in sounder with Mute function

• Probe cradle and carry handle

• Rugged all-metal case

• Curly probe lead

• Available with a range of GM, Pancake & Scintillation probes

• Count & Dose rate (cps & uSv/hr) models in stock 

• Instruction Manual (see note below) and Calibration Check Certificate Included

• NEW Optional Rugged And Original Instrument Carry Cases from £42.00 (see below) 

• External DC power & charge socket (charger and batteries not supplied). 

• Very important note: as standard the centre-pin on Mini 900 charge sockets are wired Negative (not our fault, honest...). Be warned that use of unapproved or unsuitable chargers may result in damage and will invalidate the warranty. 
  

SEE BELOW FOR OUR CURRENT STOCK BUT IF YOU WANT TO KEEP YOUR INSTRUMENT SAFE, POP BACK HERE AND CHECK OUT OUR EXCLUSIVE CARRY CASE OPTIONS

Mini Monitor 900s are as tough as old boots but that doesn’t mean you shouldn’t take good care of them. Now you can protect your instrument from the inevitable bumps, knocks and, of course, the weather, with one of our exclusive carry cases.

There are three options: On the right we have a very limited number of original (second user) leather-clad rigid over-the-shoulder cases, purpose-made specifically for the Mini Monitor 900 series. The condition is generally fair to good, but it's a case - no pun intended - of pot-luck as our supplies are low very and constantly changing. These cost £42.00 inc UKp&p

Alternatively, on the left, we have some genuine Peli Cases. These are type 1300, the original and still the best. They're second user and have led a pretty hard life, with a fair amount of scuff marks and minor scratches on the outside, but that has not affected their integrity and legendary ability to protect your Mini 900 or anything else you care to put in it, from the elements, and anything life on the road can throw at it. When new expect to pay a hundred pounds or more but you can have one of these, complete with fitted foam inserts for just £45.00 inc UK p&p.

And last, but not least, over there on the right , we have our hugely popular, and brand spanking new, super-tough IP77 rated, impact resistant carry case with fitted foam interior, soft grip handle, holes for padlocks and auto pressure release. These cases will set you back £49.99 inc UK p&p.

Please note the original cases have seen some use but they are complete, in generally good condition and supplied with the leather shoulder strap. OVERSEAS CUSTOMERS: PLEASE CONTACT US TO PURCHASE THESE CASES AND LET US KNOW YOUR LOCATION SO WE CAN  CALCULATE SHIPPING COSTS.

To add a case to your order just click chosen case on the drop-down options list.     

Please note that these cases are unsuitable for Type R, G and long-handled  'frisker' probes due to their size. Larger cases are available on request.

 PLEASE READ THE IMPORTANT SMALL(ISH) PRINT BEFORE ORDERING 

IT'S AT THE BOTTOM!

A SELECTION OF OUR CURRENT STOCK

They're Changing All The Time So Please Ask If The Model That You Require Isn't shown

(actual products shown, more pics available on request)

And by the way, we also buy Mini 900s -- any condition or quantity considered --  as well as repair and pulse-calibrate  Mini Instruments counters and ratemeters at very favourable rates. We also have a good selection of spare parts  available, just ask...

GM TUBE & PANCAKE PROBES

900/G (6062) 
Reserved

Mini Monitor 900/EL 
Tested & Ratemeter Pulse Calibrated Prior To Despatch
Typical Applications:  Environmental monitoring
Meter Scale: 0.05 - 75μSv/hr
Probe: Type: MC70, large halogen quenched GM tube
Sensitivities: Beta, Gamma X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A

900/EL (1080) 
£600.00 inc UK shipping**

Tested & Ratemeter Pulse Calibrated Prior To Despatch
Typical Applications: Alpha, Beta, general detecting/contamination control
Meter Scale: 0 – 500cps
Probe: Type: DN212, large window  halogen quenched GM tube
Sensitivities: High Sensitivity Alpha, Beta & Gamma
User-Set Threshold Alarm: Yes
Cosmetic Condition: A

£705.00 inc UK p&p**

Mini Monitor 900/E (MFG025)
Tested & Ratemeter Pulse Calibrated Prior To Despatch

Typical Applications:  low limit soft beta contamination and monitoring 

Meter Scale 0-2000 cps
Probe: type E, 25mm thin mica window compensated GM tube 
Sensitivities: Alpha, Beta, Gamma, X-Ray
User-Set Threshold Alarm:  Yes
Energy Range: Manuf. specs 
Cosmetic Condition: A

900/E 0120

£725.00 inc UK p&p**

Mini Monitor 900/E (MFG025)
Tested & Ratemeter Pulse Calibrated Prior To Despatch

Typical Applications:  low limit soft beta contamination and monitoring 
Meter Scale 0-2000 cps
Probe: type E, 25mm thin mica window compensated GM tube 
Sensitivities: Alpha, Beta, Gamma, X-Ray
User-Set Threshold Alarm:  Yes
Energy Range: Manuf. specs 
Cosmetic Condition: A

900/CSP (9001)
£500.00 inc UK shipping**

Mini Monitor 900/CSP
Tested & Ratemeter Pulse Calibrated Prior To Despatch
Probe type: Custom Nal scintillation probe, TNC connector
Typical Applications: very low level gamma detection,
contamination control
Meter Scale: 0 - 5k cps
Sensitivities: Beta, Gamma & X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A 

900/2012  5002
£500.00 inc UK shipping**

Mini Monitor 900/CSP
Tested & Ratemeter Pulse Calibrated Prior To Despatch

Probe type: Custom Nal scintillation probe, TNC connector
Typical Applications: very low level gamma detection,
contamination control
Meter Scale: 0 - 5k cps
Sensitivities: Beta, Gamma & X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A 

900/42A  
More coming

Probe type 42A 23mm Nal (T) Aluminum  window, PET connector  
Typical Applications: Gamma & enhanced X-Ray contamination control, DVT
Meter Scale: 0 – 5k cps
Energy Range: 5-150keV
Sensitivities: Gamma, X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A

900/42B  
£865.00 inc UK shipping

Probe type 42B 23mm Nal (T), Beryllium window, PET connector  
Meter Scale: 0 – 5k cps
Energy Range: 5-150keV
Sensitivities: Gamma, X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A

Typical Applications: Gamma & enhanced X-Ray contamination control, DVT

N.B A portion of the selling price of this instrument will be donated to charity

RARE MAINS-ONLY POWERED VARIANT

900/42B 7051 MAINS
More soon...?

Probe type 42B 23mm Nal (T), Beryllium window, PET connector  
Meter Scale: 0 – 5k cps
Energy Range: 5-150keV
Sensitivities: Gamma, X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A
Typical Applications: Gamma & enhanced X-Ray contamination control, DVT

N.B. Mains-only operation using internal factory-fitted 230v AC power adaptor

900/44A  9022
Reserved

Tested & Ratemeter Pulse Calibrated Prior To Despatch
Mini Instruments 900 (MFG 016)

Probe type 900/44A Nal (T), PET connector  
Typical Applications: X-Ray & gamma detection, contamination control
Meter Scale: 0 – 5k cps
Energy Range: 15 - 500keV
Sensitivities: Gamma, X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A

900/44B  

More coming

Tested & Ratemeter Pulse Calibrated Prior To Despatch
Mini Instruments 900 (MFG 017)

Probe type 900/44B 23mm Nal (T), Berylium, PET connector  
Typical Applications: Gamma &  Enhanced X-Ray detection, contamination control
Meter Scale: 0 – 5k cps
Energy Range: 5-150keV
Sensitivities: Gamma, X-Ray
User-Set Threshold Alarm: Yes
Cosmetic Condition: A+

 REALLY IMPORTANT SMALL PRINT -- PLEASE READ BEFORE OPRDERING

Unless indicated otherwise the Mini Instruments & Thermo Electron/Scientific/Morgan etc. Mini Monitor 900s that we sell are all previously owned. However, they mostly come from good homes where they have generally been well maintained, regularly calibrated and are in good working order. In addition to deep cleaning and any necessary case refurbishments, we carry out a full range of operational checks, including probe performance and HV supply, circuit board & cable inspection and pulse-calibration* (according to MI protocols and data) of the ratemeter. This is repeated immediately prior to despatch.  Most models have  fixed probe to ratemeter curly cables., a few models have factory original PET or, in a very few cases. first-user fitted TNC,  BNC or SHV type connectors. If you have a specific connector requirement we may be able to help, just ask. All models come with an unconditional  6-months guarantee.

Whenever possible we include a copy of the original user manual. We always try to ensure that they are  model-specific but in some rare cases they may be a generic version, covering basic operation and so on.  We also include a battery holder and in most cases, a vented end-window protective probe cover. Unless noted otherwise they do not come with any other accessories. Instruments are graded according to cosmetic condition from A+ to C-, with A indicating 'as-new' to very good, and C, full working order but a bit tatty or with more noticeable scratches, dinks and blemishes, etc. 

*And finally please read and understand the following: All of the instruments that we sell, maintain or repair are guaranteed to be in good working order, within factory spec and pulse calibrated in accordance with the manufacturer's protocols. However, as we cannot know how or where they will be used, or with what other equipment or materials, we cannot advise, certify or endorse them for use in regulatory, health and safety or safety-critical and related applications. If you have  a specific application we strongly recommend that you consult your RPA/RPI etc., or seek qualified expert advice before purchase. See also our Terms and Condition.

** PLUS, Vital Information For Overseas Buyers:

Hallo, Bonjour, Guten Tag, Ní hao, Namasté, Ahlan bik, Geia!, Shalóm, Hai, Kónnichi wa, Annyeonghaseyo, Szia, Salâm, Witajcie, Privét, Hola, Adaab arz hai, with apologies to anyone we’ve missed…

** PRICES SHOWN ARE FOR UK BUYERS ONLY: NON UK CUSTOMERS PLEASE CONTACT US FOR AN UP TO DATE SHIPPING COST AS PRICES ARE CONSTANTLY CHANGING...**