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4.7.3 I/O Port
The I/O port user interface (CNT) is used to monitor analog and binary input signals
and to control binary output signals. The interface has 6 inputs and 1 output. Two of the
inputs can be configured as binary counter inputs or general purpose binary inputs. There
are also 2 dedicated binary inputs, 2 analog current inputs, and 1 open-collector output. The
options for the I/O port are configured by writing to register values on the I/O board using the
MODBUS ASCII protocol.
The unit can periodically store the values of the inputs in memory. These log entries
can be read by reading the individual memory locations. Up to 224 log entries may be stored.
The logging interval can range from 1-65535 minutes.
4.7.3.1 Analog Inputs
The analog current inputs have a range from 0 to 20mA. The input impedance is
100 Ω and the ADC resolution is 12 bits. The averaging and sampling period may be
adjusted by the user. Also, alarms thresholds may be set for each input.
The ADC value stored in memory is calculated using the following equation:
ADC Value = ((12b value + addit. constant) * multiplic. constant)/1000
where the constants are programmed into memory by the user.
4.7.3.2 Binary Input
The binary input is sampled 8x per second with a sampling period of 1/64 seconds.
The active level for each binary input may be set to either a logic 0 or logic 1. The inputs may
be configured to generate an alarm when they become active. The input threshold for
detecting a logic 1 can be set at either 8uA or 20mA using a jumper on the module board.
4.7.3.3 Counter Inputs
The counter inputs have a maximum input frequency of 100 Hz. The minimum input
pulse width is 1ms. The counter input may be configured to generate an alarm when a
threshold is reached.
4.7.3.4 Binary Output
The binary output is a transistor with an open collector output. In the inactive state
(logic 0) the transistor is off. In the active state (log. 1), the transistor is on and will connect
the output signal to ground (GND). The output transistor is rated at 100 mA and 30V.
The output may be configured to generate a pulse from 125 to 8000ms in length. It is
also possible to configure the unit so that the output will become active when counter 1
(CNT1) reaches a threshold.
29
SPECTRE User Manual
SPECTRE_User_Manual_2912m
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