Glossary of Terms: M

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M
Symbol for mega (million).
m
Symbol for meter and milli- (one thousandth).
Magnetic Sensor
Sensors that are magnetically controlled by a small rotor closely positioned in front of the active sensing face. MLFK type of magnetic encoders has been designed to provide linear position information with <20 micrometers resolution. Short and medium distance applications are preferred. Advantages: non contact length measuring, no moving parts, housing sealed to IP67.  MDFK type of magnetic encoder consists of a magnet rotor and a magneto-resistive sensor. May be used just like a standard incremental encoder. Advantages: easy installation, low cost alternative to standard encoders, up/down recognition possible.
Mains
Source of electrical power, normally the electricity supply system.
Mains Frequency
Electricity ac supply frequency: 60 Hz in US , 50 Hz in UK.
Maintained Contact Switch
designed for applications requiring sustained contact after plunger has been released, but with provision for resetting.
Man Machine Interface (MMI)
Also known as human machine interface. The communication between the computer system and the people who use it.
Manual Mode
Controller does not adjust output for changes in SP or PV. Instead, the user sets the output.
Master
A device that transmits a set point signal to other controlling devices called remotes.
Maximum Error Limit
Maximum difference between measured and reference position over one 360° rotation over the full operating temperature (range).
Maximum Excitation
The maximum value of supply voltage or current that can be applied to the sensor at room conditions without causing damage or performance degradation beyond specified tolerances.
Maximum Installation Torque
 
Stainless Steel Thread M4 1.8 Nm
M5 2 Nm
M8 10 Nm
M12 20 Nm
M18 55 Nm
Brass Nickel Plated Thread M8 7 Nm
M12 15 Nm
M18 40 Nm
M30 200 Nm
Polybutylenterephthalate Thread M12 1.5 Nm
M18 3 Nm
M30 15 Nm

(Reduce torque values by 30% at the sensor’s face) The above data is valid for installations using the mounting nuts supplied with the sensor.

Maximum Load Current
The maximum amount of current that can flow through a sensor and not cause sensor failure.
Maximum Load Impedance
The largest load that the output device can operate. Usually specified in ohms.
Maximum Output Impedance
The largest load that the output device can drive while providing the full range of output.
Maximum Switching Current
The maximum permissible load current passed through the sensor.
Measurand
A physical quantity, property, or condition which is measured (e.g., pressure, temperature, flow, level, acceleration).
Mechanical Life
Life of a switch with no (or a negligible) electrical load, and a specified combination of actuation, environment and criterion of failure. Mechanical life usually is limited by the life of the switch's flexing parts and bearing surfaces.
Media compatibility
Ability to operate with a specified media carrying pressure (e.g., salt water).
Metre
The SI fundamental unit of length, equal to 1.093 yards. (Meter in US.)
Microvolt
One one millionth of a volt
Migration, Contact Material
A net transfer of material from one contact to the mating contact as a result of switching an electrical load. It usually takes the form of a needle, cone or mound or one contact face and a corresponding pit in the surface of the mating contact.
mil
One thousandth of an inch, or 0.001 inches in decimal form.
Milliampere (mA)
One thousandth of an ampere.
Millivolt (mV)
One one thousandth of a volt.
Minimum Life
An exact term only when applied to a specific group of tested switches, meaning the lowest life figure obtained from the test of that group of switches.
Minimum Load Resistance
The voltage drop across the load resistance is proportional to the current, using a sensor with current output. To ensure a proper functioning of the output stage do not exceed the maximum permissible load resistance as stated in the data sheet.
Minutes Per Repeat
Time between each repeat of proportional action by reset.
Miscible
Capable of being mixed.
Mlbs
Shorthand for 1,000 pounds of mass. The subscript m is commonly dropped and an "s" is added indicating plurality. The capital M is from the Roman numeral system where M is the multiplier x1000. This should not be confused with the "M" commonly seen in the metric system which is Mega for million.
MMBtu
One million BTUs. The M's are from the Roman numeral system where M is a multiplier of 1000. Therefore MM is 1,000 x 1,000 or 1,000,000. The M should not be confused with the metric or SI systems where M is mega for million.
MMI
Man Machine Interface (aka HMI or human machine interface). Refers to the software that the process operator "sees" the process with. An example MMI screen may show you a tank with levels and temperatures displayed with bar graphs and values. Valves and pumps are often shown and the operator can "click" on a device to turn it on, off or make a setpoint change. Examples are Intellution's FIX DMACS, Wonderware's Intouch, Genesis's ICONICS, TA Engineering's AIMACS, and Intec's Paragon.
Modbus
An industrial networking system that uses peer-to-peer communications.
Mode
Auto, manual, or remote. In auto mode the controller calculates the output based its calculation using the error signal (difference between setpoint and PV). In manual mode, the user sets the output. In remote, the controller is actually in auto but gets its setpoint from another controller.
Modular
Form of construction in which hardware or software units, often with differing functions, are quickly interchangeable.
Momentary Short Circuit
A switch with contacts that return from operated condition to normal condition when actuating force is removed. Unless otherwise stated, all switches in this catalog are momentary.
Momentary Short Circuit Protection
Output circuit protection designed to protect the output device from damage due to a temporary (1-3 sec.) short circuit or until an external fuse can interrupt current.
Momentary Switch
A switch with contacts that return from operated condition to normal condition when actuating force is removed. Unless otherwise stated, all switches in this catalog are momentary.
Multiplex Operation
In this mode two sensors may be mounted without any spacing, since they operate alternately. The response and release time of the specific sensors is therefore doubled. The connecting "control" wire must be connected to ground, if the sensor is not multiplexed.
Multiplexing
Where each signal is switched in turn to a single analog-to-digital converter. As opposed to where one A-D converter is used for each signal in simultaneous sampling.
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