Schneider Electric SR2MAN01 user manual Temperature is below 20 C

LD Language Elements

Modifying the Mode of a Coil or a Contact

To modify a contact from the front panel of the smart relay (the programming window is displayed on the screen), simply:

zPlace the cursor over the letter of the contact,

zProceed as indicated in the paragraph Modifying an element,, p. 44, to scroll through the possible contact types (A for a normally open contact, a for a normally closed contact).

Initialization	Status of the contacts and current value on initialization of the program:
	z The normally open mode (direct state) is inactive,
	z The normally closed mode (inverse state) is active.
Example		A heating resistance is to be triggered by the smart relay Q1 output when the
	temperature is below 20° C.
	A temperature probe is used, providing a 0 to 10 volt signal for a -10° to +40° C
	temperature range. A temperature of 20° C corresponds to a voltage level of 6 volts
	on the probe.
	You would write the following Ladder program:
		A1-------------				[Q1
	Using the following parameters for the A1 comparator:
			A 1		A N A L O G 5
				x 1 ≤ x 2
			R = 6 . 0			x 1 = I b
						x 2 = R
					-	+
							Menu / OK

The comparison operator no. 5 is chosen, that is ≤.

The values to compare are chosen: The analog input IB (to which the temperature probe is connected) for the first, the reference value R for the second.

The reference value is set to 6.

The analog comparator is thus active when the power measured on the analog input IB is less than or equal to 6 V. This is when the probe measures a temperature less than or equal to 20 °C.

SR2MAN01 11/2007 133