User's Manual

The RTU connectors
f
rom uC 10−Bit DAC
Amp.
AOUT
Stage 1
Fig. 14: Analog output
3.1.5 Digital Inputs
The digital inputs can be configured in several ways: First, the type of the
connected input has to be selected (Stage 1):
• When using the A740 in conjunction with a rain gauge, the “pull up” option
has to be jumpered.
• Signals in the range of 3 - 30V can be connected directly to the inputs
using the “pull down” option.
Then, the type of debouncing has to be selected (Stage 2):
• A debounce circuitry can/must be used, when the inputs will be connected
to a pulse counter and a mechanical contact (e.g. reed-contact of an Adcon
rain gauge) is used. The upper frequency limit is approximately 50 Hz.
• For signals faster than 50 Hz the debounce circuitry must be bypassed.
The maximum frequency is about 10 kHz. Fast counter or frequency input
works with clean signals only!
At last, the usage of the input signal has to be selected (Stage 3):
• Digital Input
• Counter (resolution is 16 bit)
• Frequency measurement (resolution is 16 bit). The gate time for frequency
measurement can be configured from 1 to 60 seconds (note: since the
resolution is 16 bit, the product of maximum frequency and gate time must
not exceed 65535 or the device will calculate incorrect measurement
values!).
23