Some older switches may simply be labeled “S” instead of “SR” and “D” instead of “DR”.
The analog proportional output (option B) is related to scale range (option C) and will be 4mA when vibration levels are at or below the bottom scale range. 4 mA = bottom scale range and 20 mA = top scale range
The 440 switch uses a true RMS amplitude detector and scales its output by 1.414 (RMS x v2) to give a so-called “derived peak” measurement. Because this measurement is derived from the RMS value, it will equal true peak only under the special case of a pure sinusoid, not complex vibration signals.
For dual setpoint switches, the type of output for shutdown and alarm circuits must be the same. For example, a 440-DR switch with a Triac shutdown circuit (D=0) must also use a Triac alarm circuit (E=1).
Triac output types are recommended when switching medium power rated AC devices such as motor starters, contactors, and relays. However, triacs require a 50mA holding current and exhibit a leakage current of 1mA.