Data Sheet for Product

RL 243 A Commercial Duty Analog Relay Technical Instructions
Document Number 155-107P25
Rev. 1, April, 2000
Siemens Building Technologies, Inc.
Page 5
Figure 5. Averaging Relay.
OPERATIONAL FORMULA:
TD + (T – RT) = R
Since TR = R, then
TD + T = R
2
Operation,
Continued
Averaging Relay
Output will equal average pressures at T and TD ports as long as T port pressure is
higher than TD pressure. Use with a highest and lowest pressure signal selector for
applications where either input can be the higher pressure.
Figure 6. Differential Pressure Relay.
OPERATIONAL FORMULA:
T – TR = R
Since TD is zero.
Differential Pressure
Relay
Output pressure is equal to pressure at T port less pressure at TR port.
Higher Lower Output
Input Input TR & R
T (psig) TD (psig) (psig)
20 10 15
20 6 13
20 0 10
12 8 10
10 2 6
5 3 4
R cannot be greater than S, T – TR cannot be
less than 0 psig, and T must always be
greater than TD.
Higher Lower Output
T (psig) TR (psig) R (psig)
25 10 15
20 8 12
18 6 12
17 6 11
R cannot be greater than S, and T – TR
cannot be less than 0 psig.
Discontinued