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  • Ludlum Model 177-61 Benchtop Counter

$2,020.00 $1,010.00

1 in stock

SKU: 214777261-1 Product Type: , Vendor:

The Model 177-61 is a rugged benchtop ratemeter with an alarm. This instrument is very popular for frisking operations at stations where line power is available. It can also be used in portable applications for up to 50 hours using the internal rechargeable battery.

The Model 177-61 supports GM, proportional, and scintillation detectors, and displays the results on a linear readout analog meter. The audio alarm is adjustable from 0 through 150% of full scale and is factory set to latching. Reconfiguration to non-latching can be accommodated via a minor internal change.

Front-panel controls include a four-position rotary switch for selecting each detector decade, alarm set control, audio volume adjust, fast/slow response switch, power on/off switch, and pushbuttons for count reset, battery test, high-voltage test, and alarm test. The back panel contains the power cord connection and a 9-pin type “D” plug that supports rapid battery charging, 6 to 9.6 V power output, alarm output, pulse output, and a recorder output.

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Ludlum Model 177 Alarming ratemeter.  Available in the 177, 177-45 and 177-61 models


  • 4-Range Meter
  • Linear Analog Scale Readout
  • Adjustable Alarms
  • 50 Hour Rechargeable Battery
  • Operates with GM, Proportional & Scintillation Detectors

Model 177 Series

Model 177: supports GM and scintillation detectors, linear analog meter, 4-decade range, 0 to 500,000 cpm (other dials available), adjustable audible & visual alarm (Part Number 48-1632)

Model 177-50: supports GM, scintillation, and proportional detectors, logarithmic meter, 5-decade range, 10 to 1,000,000 cpm (other dials available), adjustable audible & visual alarm (Part Number 48-1202)

Model 177-61: supports GM, scintillation, and proportional detectors, linear analog, 4-decade range, 0 to 500,000 cpm (other dials available), adjustable audible & visual alarm (Part Number 48-1382)

Model 177-84: supports scintillation and proportional detectors, dual analog 3-decade meters (alpha range 0 to 1000 cpm, beta range 0 to 100,000 cpm), independent adjustable audible & visual alarms (Part Number 48-2727)

Multi-purpose radiation monitoring, frisking
Compatible Detectors GM, proportional, scintillation
Linearity Within 10% of true value
Meter Dial 0 – 500 cpm, 0 – 2.5 kV, BAT TEST
Meter 6.4 cm (2.5 in.) arc 1 mA analog type
Multipliers x1, x10, x100, x1000
Response Time Toggle switch control FAST (2.2 s) SLOW (22 s) from 10% to 90% of final reading
Alarm Set Front-panel locking control allowing alarm to be set at any point on the meter (can be read on meter)
Reset Pushbutton to zero meter and/or reset alarm
Calibration Controls Accessible from back of instrument (protective cover provided)
Alarm Indicated by red lamp and full volume audible tone (greater than 60 dB at 61 cm [2 ft])
High Voltage Adjustable from 400 to 2500 V
Threshold Adjustable from -2 to -100 mV
Audio Built-in unimorph speaker with volume control to provide click-per-event audio or audible alarm indicator
Data Out 9-pin series “D” connector allowing for external connections of the following items:

  • Battery
  • Unregulated supply
  • Instrument common ground
  • Alarm signal (current sink)
  • Pulse out
  • External background subtract
  • Recorder output
Recorder Output Correlated to meter reading (adjustable to 1 V at 1 mA)
Power 95 to135 Vac (178 to 240 Vac available), 50 to 60 Hz, 6 V sealed lead-acid rechargeable battery (built in)
Battery Life Typically 50 hours in non-alarm condition (battery condition can be checked on meter)
Battery Charger Battery is continuously trickle-charged when instrument is connected to line power and turned on (optional external fast charger available)

Additional information

Weight 7 lbs

177, 177-45, 177-61