User's Manual

905U-K Radio Telemetry Module User Manual
 ELPRO Technologies Pty Ltd 2001 Page 16
2.5 Calculating Power Consumption
The following information may be used for calculating power consumption.
mA
Quiescent 0.10
Each radio 1.0 W Radio 350
transmission
Analogue input Externally powered transducer 10
measurement Loop Powered Transducer - 12 mA average 22
(per measurement) Loop Powered Transducer - 20 mA average 30
Pulsed Input 0 - 10 Hz (Slow Pulsed Inputs) 0.0025 x f
10 - 1000 Hz (Fast Pulsed Inputs) 0.2
w-time = warm up time in seconds f = pulse frequency in Hz
The overall power requirements may be calculated by using the above figures.
Total power per day = Quiescent
+ Pulse input (if used)
+ Analogue input per measurement x number of measurements per day
+ Radio transmission x number of radio transmissions per day
There is no additional power required for digital inputs.
Where an external battery supply is used, these figures can be used to determine the expected
battery life.
Example:-
An application has one digital input, one pulse input and one analogue input. It is powered by internal battery
supply and the analogue input uses the 905U-K loop supply. Each radio message is configured to transmit two
times.
The total power consumed = power for transmissions + power for analogue loop supply + pulse input +
quiescent
Power for radio transmissions:-
The configuration parameters, and estimated activity data, for each input are:
Digital input Update time, off state 1 day
Update time, on state 15 minutes
Input is expected to be on twice per year for 4 hours
No. of change messages per year = 2 (twice per year) * 2 (on to off and off to on)
= 4
No. of off update messages per year = 364 (approximately)
No. of on update messages per year= 2 (twice per year) * 16 (4 hours @ 15 min update)
= 32