7 replies to this topic

[panagiotis]

Hello everyone,
This is a kind of continuation of my previous post.
I would like to ask you two questions:
What are the differences between switch and transmitter? (For example temperature switch and temperature transmitter)
When we prefer to use switch and when we prefer to use transmitter?
Thank you in advance!

[Pilesar]

Some kitchen analogies... 

A common kitchen appliance is an electric kettle to boil water. These do not usually reveal the temperature of the water as it heats up. Instead, it contains a temperature switch that is activated at a preset level which cuts the power to the device after a roiling boil begins. In this case, the switch is entirely adequate for it purpose.

The electric oven in my kitchen has a digital readout which continually displays the measured temperature inside the oven. The oven temperature measurement is transmitted to the computer controller built into the oven which adjusts the heating elements to try to maintain the setpoint that the cook enters. For this service, a temperature switch would not be adequate.

[horatorres]

Switch is link with a proteccion device to the process

 

Transmitter is an indication of the process variables

 

Horacio

[panagiotis]

Pilesar I love your answer. So nice example for someone without so much of background in control-instrumentation. If I can rephrase what you said: Switch has a function to stop something in order to avoid something undesired, while transmitter "corrects something" with the help of controller.

[panagiotis]

Horattores thanks for your reply!

[fallah]

What are the differences between switch and transmitter? (For example temperature switch and temperature transmitter)
When we prefer to use switch and when we prefer to use transmitter?
 

 

Hi,

 

A Switch is normally to be applied to keep a process variable, say level, within a predefined range hence just needs to be set at mentioned range boundaries by linking to a pump keeping from running dry at below of lower range boundary and to avoid suction drum overflow at top of higher range boundary. It's obvious, no measuring is required and the switch acts intermittently when the process variable reaches to the range boundaries.

 

A transmitter, on the other hand, is normally to be applied to keep a process variable, say level, at a predefined value hence continuously measures a process variable over a range of values to feed a controller for modulating a level control valve (or for running a pump with variable speed drive) to keep the mentioned preset process variable (here level) as constant as possible.

[breizh]

Hi,

Often switches are called Dry contacts , this means they can be only in 2 positions 1or 0 over the time ,very useful to start and stop an equipment .

By comparison a transmitter delivers a continuous signal over the time , could be 4-20 mA  or 0-10 Volt ,for process monitoring.

Breizh

[panagiotis]

Thank you all for your replies ?????