# Relay Characteristic

## Relay Characteristic

a characteristic curve having a piecewise-linear shape and corresponding to the conversion by a device (or system) of a continuous input variable *x* into discrete values *y _{n}* of an output variable

*y*, where

*η*is the number of possible values or levels of the output variable; usually

*n*is equal to 2 or 3. Thus, the curve characterizes the operation of a relay.

Figure 1,a and b shows the characteristics for ideal two-step (n = 2) and three-step (*n* = 3) relay elements. Figure 1,c and d

shows the characteristics for actual relay elements. Such characteristics of actual relays have a hysteresis loop (zone of ambiguity): when *x* varies within the region *x*, ≤ *x* < *x*_{2} (Figure 1,c) or the regions *x*_{1} ≤ *x* ≤ *x*_{2} and *x*_{3} ≤ *x* ≤ *x*_{4} (Figure 1,d), the behavior of the function *y*(*x*) depends not only on the value of *x* but on the direction of the change in *x*. A value of *x* for which *y* jumps from one value to another is called an operation threshold. Figure 1,c illustrates the characteristic of, for example, simple two-step electromagnetic relays. The characteristic in Figure 1,d is exhibited by three-step polarized relays. Devices that have relay characteristics are widely used in amplitude quantizers and in relay automatic control systems.

### REFERENCES

See references under relay element.A. V. KOCHEROV