Westermo RM-115S - Manual (Page 8)

115S Serial I/O Module User Manual
Page 8 June 2011
• The Update Time is the interval in which the 115S expects to receive updates to
the Target value. The module will output enough pulses for the Count to reach the
Target within the update time. The output pulse rate is determined by the update
time, and the difference between the count and the target.
If the calculated pulse rate is more than the maximum rate (50Hz), the 115S will output
pulses at the maximum rate. At the end of the update time, the count value will be less
than the target. The 115S will then calculate the new required pulse rate for the next
update period, based on the difference between Count and Target values.
If the calculated pulse rate is greater than around three times the maximum rate, pulses
are not output. The Count value will be set to the value of the Target without any pulses
output. Pulses will be output again when the calculated pulse rate falls within the
maximum possible rate.
1.1.3 Pulsed inputs
The first four digital channels on the 115S-11 module can be used as pulsed inputs. The
maximum input pulse frequency is 1 KHz.
The pulse input channel calculates two register variables, each of which can be read by
the Modbus master.
• The Pulse Count is a count of the pulses detected on the channel since the 115S
powered up. The pulse input counts are 32-bit values (2 x 16-bit registers, a low and
a high register), and wrap around to zero on overflow.
• The Pulse Rate is a measure of the rate of pulses detected on the channel. The pulse
rate value is decimal 16,384 (hex 4000) for zero rate and decimal 49,152 (hex C000)
for the maximum rate configured by the user. These zero and maximum values are
the same as 0% and 100% used for analog values. (See section 5.4 for hex to decimal
conversion.)
The maximum pulse input rate is set during configuration. The value is in pulses per
minute and is limited to 60000 (1 KHz), the maximum rate capable of the module.
1.1.4 Analog inputs
The analog inputs on the 115S-12 can be connected as either grounded single-ended
inputs or as floating differential inputs. The 115S-12 has eight grounded inputs or four
floating inputs.
• Grounded single-ended inputs connect between the AIN terminal and the GND
terminal.
• Floating differential inputs each take up two terminals. There are four differential
pairs on the 115S-12: [AIN1-AIN2], [AIN3-AIN4], [AIN5-AIN6], [AIN7-AIN8]. For