Model 641

Radiation Survey Meter

Victoreen Model 641
The Model 641 is a commercial model radiation survey meter manufactured probably in the 1950's.
Manufactured by The Victoreen Instrument Company in Cleveland Ohio
Range of  0 - 15,000 Counts Per Second over 7 scales.
Internal Probe Case Dimensions: 7" Long  x  3¾" Wide x 9¼" Tall (including handle)
External Probe Case Dimensions: 7" Long  x  3¾" Wide x 7" Tall (including handle)
The case and top are made from aluminum. Serial Number is 110

On Left: Model 641 with external probe only case.
On Right: Model 641 with internal / external probe case.

External Probe Views
The external probe can be used with either case bottom. The probe housing contains a 1B85
Geiger-Müller tube. The probe is shown in the beta position, and retracts for gamma only.

Inside View of  Internal Probe Case
The external probe plus in on the left side in the photograph, and is wired in series with the internal probe.

Left & Right Inside Views

Front & Rear Inside Views
Left photograph shows the 3 tubes used, and the right photograph shows 2 of 3 "D" cell battery holders.

Bottom Inside View
This view shows all the batteries locations used. The NEDA 200 equivelent 67½ volt battery is on the
left, and the 3 1½ volt "D" size batteries go in the middle and on the right.
Also shown is the power supply.

Eveready No. 467 & RCA No. VS 016 are both NEDA 200 equivelent batteries.

Close-Up of Meter Face & Controls
The meter is marked only in counts per second. The controls are the scale selector switch, time constant
adjustment, discriminator adjustment and the a "Off - Hi Int - CPS - Disc" switch.

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