Operation Of 4 To 20 Outputs And Relays - HACH LANGE si629 P Manual De Uso

4. Operation

4.11. Operation of 4 to 20 outputs and Relays

Current output 4 to 20 mA depending on the pH
The analogic output offers 3 levels of different currents:
• 4 to 20 mA for measurement signal (pH or mV).
• 21 mA frozen, or the last mA value measured, when the instrument is in Hold state.
• 22 mA frozen, due to the activation of the Alarm relay (Factory settings).
Relay activation with an ON / OFF control
zone 3
RELAY L1
RELAY L1
The relays corresponding to limits 1 and 2 work in the same way. They can be configured as maxi-
mum or minimum. The relay contact is normally open, and it closes when the reading reaches the
selected ON value. The contact will open again when the reading reaches the selected OFF value.
Hence the hysteresis can be selected by the user.
Relay lag. The relays activation and deactivation lag is 2 seconds once the selected limit value is
reached.
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a b
z.2 zone 1 z.2
pH value
tendency
"on" "on"
"off"
pH value
tendency
"on" "on"
"off"
a = Factory default values
b = Example of values user-programmed
zone 3
RELAY L2
L1 = Limit 1
RELAY L2
L2 = Limit 2
Relay hysteresis L1 and L2
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