User manual
105G Wireless Gateway User Manual
Elpro_man_105g_1.18.doc Page 64
Registers which are not included in any block use the “default” sensitivity which is also user-
configurable. In the above example, the default sensitivity is 1 and is the sensitivity for all I/O
registers not included in the three blocks.
Important Note. Sensitivity values need to be selected carefully for analogue or counting
registers as small values can result in a large number of change messages, which can overload
the radio channel. A sensitivity value of 1 in 65535 is a change of 0.0015%. If the host device
writes an analogue value to a 105G every 100msec, it will change by at least 1 bit each time. A
small sensitivity value will cause a change message to be sent every 100msec. If there are many
analogue values in the same situation, then there would be many change messages every
100msec. Sensitivity values for analogue I/O should be set to be greater than the normal process
noise of the signal. For example, if a flow signal has a normal process oscillation of 2.5%, then
the sensitivity should be set to 3% (or a value of 2000) to avoid change transmissions from the
process oscillations.
4.6.2 I/O Value Scaling - Firmware version 1.76 and later:
The values in I/O registers can be scaled as the values are transferred to the data bus, or from the
data bus.
The I/O values in the 105G database registers are stored as 16-bit values (between 0 and FFFF
hexadecimal or 0 and 65,535 decimal). Analog inputs at a 105U I/O module are scaled hex 4000
(dec 16,384) for 4mA and hex C000 (dec 49152) for 20mA. A 12 mA signal is half-way in this
range at hex 8000 (dec 32,768).
The reason for adding additional scaling between the 105G database (radio side) and the data bus
is to cater for external host devices which do not handle normal 16-bit values. Two examples
are:
Honeywell Modbus gateways communicate using 12-bits values (0-4095 decimal)
Sensor / analyzer devices with “signed 16-bit” values. A signed 16-bit value is a 15-bit value
with an additional bit to signify plus (0) or minus (1).
Scaling of I/O registers can be configured in blocks. Different blocks can have different scaling.
Note that scaling only affects values transferred in or out of the data bus port. It has no affect on
the radio side.
Enable
Scaling