Model 194 Series
User’s Manual
Section 1
Ludlum Measurements, Inc.
Page 1-2 October 2020
The Model 194 is built for rugged use, featuring a well-built aluminum
body and splash-proof seals on all switches. It is also simple to use, with
no firmware or software built into the instrument.
The Model 194 can measure in units of µrem/hr (mrem/hr in the high
range) or in the SI units of µSv/h. It features a 3 ½ digit digital liquid
crystal display (LCD) with large, easy-to-read digits. A backlight toggle
switch illuminates the display under low lighting conditions.
The Model 194 detector is located inside the aluminum “can” and well
protected against shock and possible damage. The “/E” variant is built
for extremely low levels of energy. The detector extends from the
aluminum can and has a low-energy metallized polyester window to
enhance sensitivity for gamma rays in the 10-60 keV range. A vinyl cap
covers and protects the thin window when not being used.
The Model 194 is powered by two AA alkaline batteries, located in a
sealed compartment on the front panel. Battery life will depend on
many factors but is typically 200 hours under typical conditions.
There are options available to add to this instrument’s versatility,
including a headphone modification (part # 4475-118) and a shoulder
strap (part # 4475-120).
This manual encompasses the Model 194 Series, which includes the
Model 194 (µrem/hr display and internal detector), the Model 194/E
(µrem/hr display and extended detector), the Model 194/S (µSv/h
display and internal detector), and the Model 194/SE (µSv/h display
and extended detector).
