Kipp&Zonen COMBILOG Data Logger - Manual (Page 32)

4.5 Internal Processing
Next to collecting the analogue input signals, the analogue mul-
tiplexer at the input of the circuit collects the internal reference
voltage. All these values are then transmitted to the program-
mable amplifier PGA, where the signals are amplified accord-
ing to the kind and type of the connected sensors and then
supplied to the A/D converter.
The A/D converter digitalises all incoming signals with a defini-
tion of 16 bit and at a rate that can be preset for the module by
the user. The Sigma-Delta-procedure used for the A/D-conver-
sion guarantees a high accuracy and a high linearisation. The
A/D-converter processes an integrated amplifier with the ampli-
fier stages of 1, 2, 4, 8, 16, 32 and 64. For very small signals,
the module switches to an additional amplifier with amplifier
stages of 100, 200, 800 and 3200. The amplification in align-
ment with the accuracy and resolution of the calculated meas-
uring values results from the selection of the measuring range
which will be configured by assistance of the configuration soft-
ware.
This software also configures the ADC internal low pass filter,
depending on the mains frequency and desired ADC frequency
(selectable between 10 and 400 Hz). Standard configuration for
the low pass filter is 50 Hz.
The microprocessor µP now edits the measuring signal in digit-
al form.
First the processor linearises and scales the signal and holds it
ready for transmission via bus in programmable units. Further
the processor monitors the measured values for excess of
freely programmable threshold values. Thus a monitoring of
Hardware Manual COMBILOG 1022 32