18
51-650 Model 961/962 Echotel SIL Safety Manual -– Loop Version
Step
Proof Test – Echotel Model 962 Relay (continued)
5
If the unit under test fails to respond to process level changes remove the unit from the process and
bench test.
a.) Remove the unit from the process. Inspect the ultrasound transducer for evidence of damage or
coating buildup. Fouling on the transducer surface may interfere with normal operation. If heavy
fouling is evident, it is suggested to service the transducer more frequently.
b.) Clean the ultrasonic transducer, especially in the area of the sensor GAP.
c.) Perform a bench test per the steps of section 4. When possible it is best to use the actual
process material, because materal properties affect the ultrasonic performance. Confirm proper
unit operation: WET/DRY GAP condition; LEDs and Relay contacts state.
d.) If unit passes the tests of steps 5c, return to the process installation and repeat the tests of
step 4.
e.) If the unit fails re-test in the process, it must be replaced
6
Proof test is complete. Restore loop to full operation.
6.1.5 Proof Test Coverage
The Proof Test Coverages for the various product configura-
tions is given in Table 5.
Table 5
Device
Proof Test Coverage
Line-Powered, Relay Output Version
Loop-Powered, Current Shift Version
961 Dry Is Safe
89%
14%
961 Wet Is Safe
81%
64%
962 Dry Is Safe
74%
68%
962 Wet Is Safe
71%
86%
