Setting Thresholds - Fluke 35040 Operator's Manual

Q represents the next sample of charge at time T
1
the interpolated charge at time T
within the range: T < T
1 2
Predicted Timed Charge and Dose
This measurement extrapolates the timed charge (Q
accumulated at completion of the timer interval (i.e., TimerIntervalSetting) based on the rate of charge
delivery.
Q [C]
Timed
=
Q
Timed_Pred icted
T [s]
Elapsed
=
Dose Q
Timed_Pred icted Timed_Pred
At the conclusion of the timer interval (i.e., T
charge and dose are equal to the predicted timed charge and dose, respectively.
Accumulated Charge and Dose
This measurement accumulates charge across multiple exposures. The displayed value is updated
during the exposure and held between exposures. It is reset to zero when the RESET/MEASURE button
is pressed while viewing a measurement screen.
=
Q Q
Accum Accum _ previous
=
DoseAccum Q [C]
Accum
Exposure Current and Rate
The current (3-1/2 digit) and dose rate displayed when the exposure is in progress are updated once per
second. The current and dose rate return to zero after the end of the exposure. The dose rate
measurement is displayed using the selected time base (seconds, minutes, or hours). If the start and
stop thresholds are set to zero, I
= −
I I [A] I
Exposure Leakage
DoseRate = I [A]
Exposure
Average Current and Rate
The average current is calculated using the charge accumulated (
eliminate noise effects. The displayed value (4-/1/2 digit) is held following the exposure and reset at the
⎛ ⎞
−
Q [C] Q [C]
2 1
= ⎜ ⎜ ⎟ ⎟
I
Avg
−
⎝ ⎠
T [s] T [s]
2 1
DoseRateAv g = I [A]
Avg
start of a subsequent exposure.
Q and Q are measured within the exposure at times T
1 2
start of exposure. T is 1.33 seconds before the end of exposure (see Figure 2-3). The exposure must be
2
more than 3 seconds long. I

2.3.1 Setting Thresholds

The instrument has capability to automatically detect the start and end of an exposure when the current
crosses given limits. Using automatic detection eliminates the sag in readings that occur due to leakage
, where T is an integral number of seconds that is restricted to times
2 2
≤ (T
+ Timer Interval Setting).
1
×
TimerInter valSetting [s]
×
[C] ICCF [Units/C]
icted
Elapsed
+
[C] Q [C]
Exposure
× ×
ICCF [Units/C] ADCF
is zero.
Leakage
[A]
× ×
ICCF [Units/C] ADCF
× ×
ICCF [Units/C] ADCF
is 0 if the exposure is less than 3 seconds.
Avg
following the activation of the timer. Q
1
) at the elapsed time (T
Timed
×
ADCF
equals the TimerIntervalSetting), the predicted timed
×
RateMultip lier [s]
/ )
Q
during a portion of the exposure to
t
×
RateMultip lier [s]
and T respectively. T
1 2
Theory of Operation
Basic Operating Equations
corresponds to
2
) that should be
Elapsed
is 1.33 seconds after the
1
2
2-7