Vaisala DRYCAP DMT345 Guía de usuario descargar pdf (Pagina 113)

Chapter 4 ________________________________________________________________ Operation

VAISALA ______________________________________________________________________ 113

Mode 4 is usually used if an alarm needs to be triggered when the

measured value exceeds a safe range. The relay is active when

measurement is in range, and is released if the value goes out of range or

the measurement fails.

NOTE

If the measurement of the selected quantity fails or the transmitter loses

its power, the relay is released.

Hysteresis

Hysteresis function is to prevent the relay switching back and forth when

the measured value is near to the setpoint values.

Relay is activated when the measured value passes the exact value of the

setpoint. When returning and passing the setpoint again relay is not

released before the value reaches the setpoint increased/decreased by the

hysteresis value.

Hysteresis should be smaller than difference of the setpoints.

Example:

When the 'active above' value is 50 ºC and the hysteresis value is 2 ºC,

relay activates when the relative humidity reaches 50 ºC. As the humidity

then decreases, relay releases at 48 ºC.

>rsel tdf ts

Rel1 Tdf above: 0.00 'C ? 50

Rel1 Tdf below: 0.00 'C ? -

Rel1 Tdf hyst : 0.00 'C ? 2

Rel1 Tdf enabl: OFF ? on

Rel2 Ts above: 0.00 'C ? 80

Rel2 Ts below: 0.00 'C ? 60

Rel2 Ts hyst : 0.00 'C ? 1

Rel2 Ts enabl: OFF ? on

NOTE

If both setpoints are specified and "above" setpoint is lower than

"below" setpoint, the hysteresis works in the opposite direction, that is,

relay is released when the measured value passes the exact value of the

setpoint.

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Vaisala DRYCAP DMT345 Guía de usuario Pagina 113