Greyline Instruments SLT32 - Noise Prevention Strategies; Noise Suppression on Relay Output

Avoidingnoiseproblems
1.ItisrecommendedthatelectronicinstrumentsbeconnectedtoarelativelycleanACpowersource.
UseanACpowerfilterorisolationtransformerifnecessary.
2.Thesensorinputlineandthecontrollines(ACorDC)shouldnotberuninthesameconduit.The
sensorinputshouldbeseparatedfromwiresgoingtoinductiveloadssuchasmotors,solenoids,relays
andcontactors.Forbestresultsrunthesensorwireinaseparatemetalconduit.Atwo-conductor
shieldedcableisrecommendedforthe4-20mAoutput,theshieldshouldbeconnectedtochassisground
attheinstrumentonly.
3.Fortherelayconnections,oneofmostoverlookedsourcesoftrouble,noisesuppressorsare
recommended.Alsoknownas“snubbers”thesedeviceswilllimitthelargespikesproducedwhenthe
relayopens,stoppingtheRFIandalsoprotectingtherelaycontactsfromdegrading.
SLT32Level&FlowMonitor
ManualSeriesB.11
Page 30
C
NO
NOISE
SUPPRESSED
AT INSTRUMENT
POWER
240VAC (MAX)
28VDC
NOISE
AT LOAD
(
BEST)
SNUBBER
GREYLINE PART# SNUB
SNUBBER
LOAD
GREYLINE
INSTRUMENT
NOISE SUPPRESSIONONRELAY OUTPUT
SUPPRESSED