F&H Models FH 40H and FH 40 Tv (1950s and 1960s)
This particular instrument, manufactured by Frieseke and Hoepfner of Germany, was used by the U.S. Atomic Energy Commission's Chicago Operations Office. As can be seen in the following photographs, the FH 40H "Radiameter" came in a wooden case containing two drawers that were loaded with accessories: a variety of GM tubes (all glass wall), extension cables, external probes and extra batteries.
Quoting the instrument manual: "The radiation measuring instrument FH 40H "Radiameter" serves for measuring the intensity (dose rate) of gamma radiation and X-rays and detecting of beta rays as well as alpha rays when certain accessories are applied."
It has two ranges: 0-25 mR/hr and 0-1 R/hr.
In the standard mode of operation, the detector (a short GM tube) is located in the top of the meter. Four curved slots (see photo below) serve as the radiation entrance window. If desired, a beta shield can be rotated in front of the tube by turning the clear plastic knob on the right side of the meter case.
The mode of operation is a little unusual in that it is a GM detector that employs a zero adjust (the black knob "Batt. alt").
The photograph to the left shows an F&H 40Tv distributed in the US by Kahlsico of El Cajon California. A 1963 product description states that the FH 40 Tv "is easy to use—even by inexperienced personnel—because by turning a single knob one changes circuitry, measuring scale range and GM tube shielding... Instrument uses two counter tubes: one for gamma measurements over the ranges 0-0.5 mR/hr, 25 mR/hr and 1 R/hr and for gamma and beta determinations in the ranges 0-320 0r 0-10,000 cpm; and the other for gamma measurements only in the range 0-50 R/hr."
The FH 40 Tv incorporates a neat feature also used in the AN/PDR 27 RADIAC meters: the range switch (a black knob on right side of case) changes the displayed scale when it is turned. In other words, it is almost impossible to mistake the scale that is being read.
The knob below the range switch is the zero adjust control.
Case: ca. 3 3/4" x 6 3/4" x 1 1/2"
- F&H Description and Operating Instructions for FH 40H, no date.
- Product description for FH 40Tv. Nucleonics April 1963, page 84.