Portable Survey Instruments
ANSI N317 (ANSI, 1980a) discusses several criteria related to the
performance of portable survey instruments; these include the following
-- The overall accuracy shall be within ±20%, and the precision shall be
within ±10% at the 95% confidence level.
-- The response time (i.e., the time for the instrument reading to go
from zero to 90% of full scale) shall be < 10 seconds on the most
sensitive scale and < 2 seconds at readings of 100 mrem/h, 100
mR/h, and 500 dpm or greater. (This criterion is unrealistic with
current neutron instrument capabilities. Response time is typically 30
to 60 seconds.)
-- The instrument shall be able to maintain accuracy and precision for a
minimum of 24 hours of continuous operation.
-- The instrument shall have a minimum battery lifetime of 200 hours
of continuous operation.
ANSI N42.17A (ANSI, 1988a) specifications differ slightly.
-- The response of the instrument shall not change by more than ±15%
from a reference value taken at 20°C over the anticipated
temperature range for operation.
-- The instrument system shall function within specifications over all
anticipated combinations of temperature and humidity (e.g., 15° to
65°C, 40% to 95% relative humidity).
Photon survey instruments should meet the accuracy requirements
stated in ANSI N317 (ANSI, 1980a) over the energy range of 0.01 to
1.25 MeV. The angular response of this type of instrument should be
within ±15% over a 2 π steradian frontal direction using at least two
photon sources with energies ranging from 0.06 to 1.25 MeV.
Experience has shown that this response specification is not met by most
instruments at lower energies due to attenuation of the photon. The
energy dependence should be within ±15% over the range of very low
energy to 1.25 MeV and the operating range should be from 0.5 mR/h to
at least 5000 mR/h.