Adjustable Ratio Relay Fairchild Industrial Products

Adjustable Ratio Relay

Fairchild's Model 21 is an Adjustable Ratio Pneumatic Relay, whereby the ratio of output pressure to signal pressure is infinitely adjustable. The adjustment range permits signal amplification of 1:30 or signal reduction of 30:1 by rotation of the ratio adjustment knob. The Model 21D is available with both input and output adjustable bias. Maximum input bias is 3 psig, with a maximum output bias of 9 psig.

Adjustable Ration Relay (M21)

The Model 21 Adjustable Ratio pneumatic relay has a signal chamber lever arm, whereby the ratio of output pressure to signal pressure is infinitely adjustable. The Model 21D is available with both input and output adjustable bias. Maximum input bias is 3 psig, with a maximum output bias of 9 psig. The basic mathematical expression for the bias in this relay is Po = (Ps-K1) R+K2, where Po = Output pressure, Ps = Input signal, R = Ratio of setting, K1= Input bias, (-) only, and K2 = Output bias, (+) only.