Chapter 6 Mechanical Input Control Devices

Push button

An industrial ______ consists of a legend plate, an operator, and one or more contact blocks (electrical contacts).

barometer

A _____ is not a common sensing device used by most pressure switches.

joystick

A _____ is used to control many different circuit operations from one location.

capacitive

A _____ level switch detects the dielectric variation when the product is in contact with the probe and when the product is not in contact with the probe.

mechanical

A _____ level switch uses a float, which moves up and down with the level of the liquid and activates electrical contacts at a set height.

conductive probe

A _____ level switch uses liquid to complete the electrical path between two conductive probes.

cam-operated

A _____ limit switch must be installed to prevent severe impact and allow a slow release of the lever.

pressure

A _____ relief valve may be added to a circuit to protect a pressure switch from excessive pressure.

DMM

A _____ set to measure voltage is used to test the operation of a switch.

pressure

A _____ switch is a control switch that detects a set amount of force and activates electrical contacts when the set amount of force is reached. One psi equals 27.68in. WC

flow

A _____ switch is a control switch that detects the movement of a fluid.

limit

A _____ switch is a mechanical input that requires physical contact of the object with the switch actuator.

foot

A _____ switch is used to allow handsfree control or an additional control point. Two positions

flow

A _____ switch may be used to advance a clogged filter when restricted airflow is sensed.

push roller

A ______ actuator is an actuator operated by direct forward movement into the limit switch.

contact pole

A ______ is not a basic actuator used on limit switches.

three-position

A ______ selector switch allows the operator to select one of three circuit conditions.

two-position

A ______ selector switch allows the operator to select one of two circuit conditions.

selector

A ______ switch is a switch with an operator that is rotated to activate the electrical contacts.

jumbo mushroom button

A(n) ______ operator can be operated from any angle and is used in applications that require fast operation such as emergency stops, motor stops, and valve shutoffs.

operator

An _____ is the device that is pressed, pulled, or rotated by the individual operating the circuit.

actuator

An _____, such as a lever, fork lever, push roller, or wobble stick, is the part of a limit switch that transfers the mechanical force of the moving part to the electrical contacts.

truth

Contact position on a selector switch may be illustrated using _____ tables (target tables) or solid lines, dashed lines, and a series of small circles.

Piston

Cylindrical device that is moved back and forth in a tight-fitting chamber by the pressure applied in the chamber.

Bellows

Cylindrical device with several deep folds that expand or contract when pressure is applied.

Diaphragm

Deflecting mechanism that moves when a force is applied.

cooling

In a _____ system, cool air is produced when the temperature switch contacts heat and close.

heating

In a _____ system, heat is produced when the temperature switch contacts cool and close.

mounted

Limit switches should be ______ in a way that prevents accidental activation, accumulated materials, and excessive heat.

sensing devices

Pressure switches use different ______, including diaphragms, bellows, and pistons, to detect the amount of pressure.

hoist

The most common application of a joystick is in controlling a _____.

Deadband

_____ is the amount of pressure that must be removed before the switch contacts reset for another cycle after the setpoint has been reached and the switch has been actuated.

Resistive

_____ loads are the least destructive loads to switch.

Arcing,Welding

_____ or _____ of the contacts may occur from a possible short circuit if the contacts are connected to opposite polarity

Limit

_____ switches are used to convert a mechanical motion into an electrical signal.

Level

_____ switches detect and respond to the level of a material in a tank The distance controlled in one-level control is small, but any distance may be controlled in two-level control.

Contact blocks

______ include normally open (NO), normally closed (NC), or both NO and NC contacts.

Contact protection

______ should be added when switching large DC and AC inductive loads to prevent or reduce arcing at the switch contacts.