Dewetron DAQP-CHARGE-B Series, Техническое справочное руководство

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DAQP-CHARGE-B
DEWE-DAQP-CHARGE-B
9
pin
male
SUB-D
Output
to
A/D
card
SW1
SW2
LEDS
J1
ON
OFF
ISOLA
TION
Power consumption
Charge is defined by current multiplied with time (Q = I x t). That means that every charge amplifier (or
better: charge to voltage converter) requires more power if the charge amplitude or the frequency increases.
The relation between power, charge and frequency is definend by:
[ ] [ ] [ ]
-11 10 × 6.28 × Hz f × pC Q = W P
That means that the DAQP-CHARGE-B requires 6.28 W at 100 kHz and 1 000 000 pC of additional power
(or 0.628 W @ 10 kHz and 1 000 000 pC). But the internal amplifier (and also the DEWE-RACK) is limited to
2 W for additional power.
Although this limitation the DAQP-CHARGE-B can also used with a 100 kHz and 1 000 000 pC signal for a
short time. Up to 50 cycles with that high frequency can be handled without any limitation. After this 50 cycles
it is necessary to have a break of at least 100 cycles to be within the maximum average power consumption.
Isolation
The DAQP-CHARGE-B series module offers
an isolation between input and output (= factory
default). This will eliminate nearly all errors which
occur if the input GND (= sensor GND) has not
exactly the same potential than the GND of the
data acquisition system.
Different locations have different potential.
Therefore errors may occur if many sensors are
mounted on different locations.
But if the ground of the charge sensor is isolated
or the potential where the sensor is mounted is floating better results can be achieved if the module input
GND is connected to the module output GND. These can be done externally, but also with two internal
jumpers. Set both jumpers to the lower position to connect the input and output GND and disable the
isolation.