Emerson manual Rosemount 848L, Reference Manual, 00809-0100-4696,Rev AA September

Reference Manual

00809-0100-4696, Rev AA September 2004

Rosemount 848L

Rung L1 is equation 1. It latches on when the start button is true and unlatches when the NC stop button is pushed. The latch remembers start and stop commands to simplify the logic.

•The expression is RS(IN(2),NOT(IN(1)));

Rung P1 is equation 2, which generates a pulse from one read of channel 5:

•The expression is TON(AND(OR(IN(3),IN(4)),NOT(EQ(2))),30000);

Rung L2 is equation 3. The latch determines which motor to start and run. It toggles when the life time is reached. That stops the running motor (after its off delay) and enables the other motor to be started.

•The expression is RS(AND(EQ(2),NOT(EQ(3)),AND(EQ(2),EQ(3)));

Rung Out1 is output equation 1. A timed start pulse is delivered to both motor circuits when either the start button is pressed to set the Run latch or the end of the hour count toggles the selector latch. Only the enabled circuit will start. The output resets the external timer.

•The expression is TP(OR(RISE(EQ(1)),EQ(2)),20);

Rung Out2 is output equation 2. Power goes to the external timer while either confirm is true, but not during reset.

•The expression is AND(OR(IN(3),IN(4)),NOT(OUT(1)));

Rung Out3 is output equation 3. This is basic motor control with an off delay of 5 seconds to maintain flow.

•The expression is TOF(AND(EQ(1),NOT(EQ(3)),OR(OUT(1),IN(3)),50);

Rung Out4 is output equation 4. This is also basic motor control with an off delay.

•The expression is TOF(AND(EQ(1),EQ(3),OR(OUT(1),IN(4)),50);

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