Fluke Biomedical 1060AM - Manual (Page 22)

Victoreen 1060AM
Operators Manual
4-2
4.1.7 Digital inputs
There are 16 TTL level digital inputs with pull up resistors. They may be used to indicate the state of
various process conditions. All are read by software.
4.1.8 Digital outputs
There are 16TTL level digital outputs under software control. They may be used as input signals to drive
process equipment.
4.1.9 Communication
The software transmits parallel data from the microprocessor to the Dual UART that converts it to serial
data and controls the transmission to external devices. Two RS-485 serial channels are provided. These
channels are for multi-drop communication. There is one RS-232 port for local communication.
4.1.10 Engineering Units
The software will convert raw counts to any engineering unit that the Model 1060 has been programmed
and calibrated for. Raw counts as well as converted units can be combined to provide appropriate
engineering units.
4.1.11 Error Analysis
From the sensitivity of the detectors and the Gaussian distribution statistical model for radioactive decay
measurements, the measurement error can be calculated directly as a function of exposure rate and the
counting time for each detector.
For this distribution the standard deviation is the square root of the number of counts ( =√Total Counts).
The total number of counts is equal to the exposure rate times the tube characteristic times the total
counting time (Total Counts = Exp. Rate x Tube Char. x Time). The total counts is the mean or expected
measurement.
It is also given for Gaussian distributions that 99.73% of the actual measurements will fall within the mean
plus or minus three standard deviations (μ ± 3s). This is then chosen as the error range.
From the above discussion the accuracy of any detector can be computed.
4.1.12 Minimum Detectability
Minimum detectability, in the presence of a radiation background, is usually calculated at the 50% and
95% confidence level. A good first approximation to each is as follows: First, determine the mean and
standard deviation of the background. Look up the sensitivity of the detector to the nuclide. Factor in any
geometry efficiency. The 50% confidence level is the activity level, accounting for geometry and
sensitivity, of the nuclide at the mean plus three standard deviations of the background. For the 95%
confidence level use the mean plus 4.645 standard deviations of the background.
4.2 Functional Description
To be provided later.
4.3 Circuit Description
To be provided later.