Dose rate indication is provided in digital and analog form simultaneously. The analog scale covers two
decades and consists of 32 bar graph segments arranged in the shape of an arc. Two adjacent ranges
always overlap by one decade. To make operation as easy as possible, the 6150AD automatically
switches ranges including the analog scale, the decimal point, and the unit. A short sound calls the user’s
attention every time the range was switched.
The main display is the digital display. The analog display serves merely to indicate trends because the 32
bars over two decades do not allow very accurate readings.
The 6150AD calculates and displays dose rate at one-second intervals. The one-second cycle was chosen
for ergonomic reasons. Faster changes of the display, particularly of the digital display, would be difficult
to read and would strain the user’s eye. You have to consider the one-second cycle when trying to look
for changes in dose rate. The instrument will not notice a radiation source if you move it rapidly past that
source. You have to concede the instrument at least several cycles, that is several seconds, to notice the
source. The time required to indicate the new dose rate value depends on the amount of change in dose
rate referred to its initial value. The microprocessor will assist you by adjusting response time in the best
way according to the rules of statistics. Section 10 contains more information on response time.
Audible Single Pulse Detection
Audible single pulse detection enables you to »hear« the pulses. This can be particularly helpful to detect
changes in dose rate. Therefore audible single pulse detection is enabled after switching the instrument
on. It may be disabled by pressing the signal key. If the loudspeaker symbol in the upper right corner of
the LCD is visible, audible single pulse detection is enabled.
Note that the piezo buzzer cannot emit more than approx. 15 clicks per second, whereas at high dose
rates much more than 15 pulses per second occur. This means that the frequency of the clicks only
reflects a small lower portion of the dose rate range. Therefore, do not try to estimate dose rate from the
click frequency; the clicks just provide an acoustic aid at low dose rates.
As soon as dose rate reaches or exceeds the dose rate alarm threshold, the instrument issues dose rate
alarm in both audible and visible form. The alarm tone is an intermittent one (two sounds per second),
and the flashing loudspeaker symbol in the LCD takes the visual part (with /E models, the analog scale
divisions additionally flash to make the alarm even more visible). Pressing the signal key will put the
alarm tone out, whereas the symbols will continue to flash. As soon as dose rate drops below the
threshold, audible and visible warnings disappear automatically.
The 6150AD will issue dose rate alarm only in the »dose rate indication« state. You have to set the
6150AD1/2 to that state to realize a dose rate alarm. The 6150AD3/4/5/6, however, automatically
switches to the »dose rate indication« state as soon as a new dose rate alarm occurs. Therefore the
6150AD3/4/5/6 prevents a dose rate alarm from being overlooked, even if at the time of its occurrence
the instrument was in some other state.
All 6150AD models have several fixed dose rate alarm thresholds one of which the user can select. The
6150AD3/4/5/6 additionally provides a user programmable threshold, see section 12.1.
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