Rockwell Automation 1425 PowerMonitor Wireless 250 - Manual (Page 44)

44 Rockwell Automation Publication 1425-UM001A-EN-P - January 2012
Chapter 3 Software Interface
Comments on RF Communication Configuration and Status
The following sections provide comments on the RF communication
configuration and status tables.
Hop Count (register 201)
This register reports the number of network node hops taken by a packet
delivered from the device to the PC Receiver. A device with a hop count equal to
1 is communicating directly with the PC Receiver.
For hop counts greater than 1, the First Hop ID (register 202) and the Last Hop
ID (register 203) report the device ID of respectively the first Router and the last
Router on the path used by a packet to get to the PC Receiver.
Radio Signal Strength Indicator, RSSI (register 204)
RSSI value is stored in the high byte of Register 204 and can be either positive or
negative (signed integer).
When negative, the value is expressed by using 2's complement. The following
table shows some examples of RSSI representation and the significance of the
values.
The second byte of register 204 is the battery voltage raw data, which can be
converted into voltage value in decimal as follows:
Battery Voltage = (1.225*1023.0)/(blRaw+344)
where blRaw is the raw value in decimal. For instance, a battery reading of 0x19
(2nd byte of register 204) would be 25 in decimal, then Battery Voltage =
(1.225*1023) / (25+344) = 3.3961V.
Table 24 - RSSI Register 204
RSSI Value Register 204 Low Byte in Decimal
(hex) Signal Strength Category
≥-20
236 (0xEC) Strong
-20…-35 236 (0xEC)…221 (0xDD) Good
-35…-45 221 (0xD)…211 (0xD3) Weak
< -45 211 (0xD3) Not acceptable