Sentec GmbH - Strahlenmesssysteme

                  Nukleare Messtechnik

Qualität und Erfahrung seit über 20 Jahren!


High Temperature Measuring Device

with Geiger-Mueller-Counters

Gamma-Energy range 0.1 - 7 MeV


- Qualified according to the German KTA3505

- Separation of detector and preamplifier

- Logic signal

- Discriminator

- Long term temperature range up to 75oC

- Short tern temperature range up to 125oC

- Humidity up to 100% with dewing

- Vibration/Shock proofed

- Driver for signal transmission up to 400 meters

- Internal stabilisation against voltage drifts

- Warranty for operation in extreme conditions

by special selected components

- Direct connection to secondary electronics for pulse



"N-16"-measuring for leakage monitoring along the steam-

pipes of nuclear power plants for low to high energy gam-

mas (<2,5 MeV) from N-16.

Countrate measurements at high temperatures e.g. in geological survey (drill hole measurements etc.)


The system GM175A is typically used in regions with elevated temperatures. By spacial separation from detector head the preamplifier electronics is protected from damages caused by excessive temperature in the detection area.

Highly qualified components allow higher temperatures

compared to comparable instruments.

The compact design of the detector head and the transmission of the signals over distances up to 400 m makes the system ideal for installations at inaccessible regions or at hot and contaminated areas.

The resulting signals are directly transmitted to succeeding

electronics (e.g. for shutdown at elevated radioactive levels) or for countrate measurements.

The system GM175A consists of

detector DG175A,

preamplfier VG175A,

system cable SC175A.

Principle of Measurement:

By interaction of gamma rays with electrons in the counter tube gas results in secondary ionisation within the gas which is unloaded at the anode and results in a voltage pulse to be transmitted accross the system cable to the preamplifier circuit where it is shaped.

Technical Data

Input high voltage/supply voltage

High voltage/maximum:              1400 V positive

High voltage/operating voltage:  1250 V positive

Power consumption/maximum:  0.25 W when counter tube shorted

Power consumption/typical:        typ. 2*1.44 W

Preamplifier supply voltage:       typ. + 18 V/80 mA

Socket:                                       Fischer DBEE 105 A 096-11

Output Logic signal

Amplitude:                                  5.0 + 0.5 V in 75 ohms 

Pulsewidth:                                 500 + 200 ns (FWHM) 

Risetime:                                    5-100 ns (10% - 90%) 

Pulseshape:                                rectangular

Polarity:                                      negative (opt. positive) 

Impedance:                                 75 + 10 ohms  

Socket:                                       Fischer DBEE 105 A 005-11       


Overload Protection:                   0 - 1200 mV

                                                    factory set on request

Operation conditions

Long term temperature range                  10 - 75oC

Short term temperature range                75 - 125oC

Temperature gradient for detector           ≤ 4 degree/min.

Pressure resistance                                 0.7 - 1.3 * 105 Pa

Long term humidity                                  95% without dewing

Short term humidity                                 100% with dewing           

Background countrate (at 0,1 μSv/h) < 2.0 cps



Frequency range 5 to 35 Hz:               6g, 1 oct/min.

                              35 to 100 Hz:             12g, 10 oct/min.


30g, 11ms for all components of the system

Magnetic Shielding

Influence of the earth magnetic field is negligible for all directions

Radioscreening                         acc. VDE 0847

Electrical protection                 IP 65 acc. DIN 40050

Mechanical Assembly

(housing from stainless steel)

- Detectorhead DG175A with

Geiger Mueller counter tube SBM13

Length:                          347 mm

Max. diameter:                45 mm

Weight:                          about 0.9 kg

- System cable SC175A

(connection detector - preamplifier)

Length:                          4-8 m

- Preamplifier VG175A with


Pulse shaping electronics,

Internal generation of supply power,

Driver stage

Length:                          250 mm

Max. diameter:                94 mm

Weight:                          about 2.5 kg

Possible connections to secondary electronics

(not part of the system; test cable optional)

Signal cable

(Connection signal output - secondary electronics)

Cable:                            shielded coaxial cable

Mantle diameter:            9.1-10.5 mm

Max. length:                   400 m

Impedance:                    75 Ohm

Connector at preamplifier: Fischer SE 105 A 005-11

Supply cable

(Connection supply input - secondary electronics)

Cable:                            8 wire cable with 1 shielded coax                                                  and 7 trip lines

Mantle diameter:            9.1-10.5 mm

Max. length:                   400 m

Connector at preamplifier: Fischer SE 105 A 096-12

Test cable PK1

(Connection signal output - test devices)

Cable:                            BNC coaxial cable 75 Ohm

Mantle diameter:            9.1-10.5 mm

Max. length:                   10 m

Connector:                     Fischer SE 105 A 005-11 to BNC
















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