5
8.0 Data Input and Output
The SAAFShield Detecting Unit control logic interface block interprets
the 4-20 mA signal originating in the SAAFShield Communications
Module and produces a set of data consisting of each piece of data
collected by the SAAFShield detecting unit. The block also has some
failure detection capabilities. If a failure is detected the Fail bit is set
and a fail code is populated.
Block Diagram
SAAFShield
Communications
Module
FAL
CumCu
CumAg
IncCu
IncAg
RH
Temp
Error
In
Qui
Rst
Inputs
Parameter Name Type
Description
In
DINT
Physical IO Tag
Qui
Boolean Signal Quality
Rst
Boolean Initialize output to starting values
Notes:
The range and unit of measure for all metal readings is 0 – 4000 angstroms.
• Relative Humidity is measured 0 – 100%.
• Temperature is measured -50 – 150º C
Pulse Codes
Variable
Number
Pulse Level
Length
of Pulses
(raw value)
of Time
Start Signal
1
6.28 mA or 16486
3 seconds
Inter-data Pulse 2
8.58 mA or 22486
1 second each
Data Transfer
1
N/A
5 seconds
Details
Parameter Name Type
Description
FAL
Boolean True if QUI is False
CumCu
DINT
Cumulative Copper reading in angstroms
CumAg
DINT
Cumulative Silver reading in angstroms
IncCu
DINT
Incremental Copper reading in angstroms
IncAg
DINT
Incremental Silver reading in angstroms
RH
Real
Relative Humidity reading
temp
Real
temperature reading
error
Real
error Code
Cycle
every 15 minutes the SAAFShield Communications Module sends data
to the analog input (SigIn). It sends the start signal for 3 seconds, waits
2 seconds, and then begins data transmission. each measurement
is transmitted for 5 seconds. there is a two second wait followed by
two inter-data pulses. Then the next measurement sequence is
transmitted. The chart below (Figure 6) shows an example sequence.
Note that all data transmitted is set high. When the Communications
Module has sent all pieces of data, it waits for 15 minutes before
beginning the cycle.
Steps
1. Send one 6.28 mA pulses of 3 seconds.
2. Wait 2 seconds.
3. Transmit Cumulative copper data in the range of 4-20mA
for 5 seconds.
4. Wait 2 seconds.
5. Send two 8.58 mA pulses of 1 second each with inter-pulse
pause of 1 second (set loop to 4mA during pause)
6. Wait 2 seconds.
7. Transmit Cumulative silver data in the range of 4-20mA
for 5 seconds.
8. Wait 2 seconds.
9. Send two 8.58 mA pulses of 1 second each with inter-pulse
pause of 1 second (set loop to 4mA during pause)
10. Wait 2 seconds.
11. Transmit incremental copper measurement in the range of 4-20mA
for 5 seconds.
12. Wait 2 seconds.
13. Send two 8.58 mA pulses of 1 second each with inter-pulse
pause of 1 second (set loop to 4mA during pause)
14. Wait 2 seconds.
15. Transmit incremental silver measurement in the range of 4-20mA
for 5 seconds.
16. Wait 2 seconds.
17. Send two 8.58 mA pulses of 1 second each with inter-pulse
pause of 1 second (set loop to 4mA during pause)
18. Wait 2 seconds.
Figure 6.
