Sensor measurement

Sensors are the artificial senses that help us perceive. Smart sensors go a little further than the yellow mailbox alert flag that tells us whether the postman has come by. Predicting a tsunami, measuring radiation levels, or signalling a faulty underground piping requires innovation and high quality sensors.

Sensors are designed to work electronically or mechanically. Analyzing measurements provides a wealth of information, for this we refer to our article on data analysis.

Standard industrial sensors

Although sensors come in many shapes and sizes, there are similarities. Most sensors have a similar output signal, or a standardized method for reading the measured values. We call these the standard industrial sensors.

Generic sensor reader

Standardized output signals make sensors widely applicable and usable for “system integrators”. It also means that a “reader” can be somewhat generic, capable of reading many types of sensors. And that is exactly the subject that Mobeye has specialized in.

The most common output signals

Potential-free sensors

A potential-free sensor can best be described as a contact that can switch “open” or “closed”. This group includes switches, magnetic contacts and relay contacts.

An example of a potential-free sensor is a magnetic contact, with the fixed part attached to the door frame and the magnetic part to a door. When the door is closed, the two parts are close together and the contact is closed. When the door opens, the two parts separate and the loop is opened. The fixed part (on the door frame) has a metal part internally, which is bent by the magnet and thus acts as a switch.

A relay is a special type of switch that switches when it is powered. The magnetic field flips the switch. Where the input voltage can differ per relay, the output signal is always potential-free.

Analog sensors

This group includes sensors with a “voltage” output. Sensors usually have a range between 0V and 1V, 0V and 5V, 0 and 10V, or 4-20mA.

As an example we take a specific pressure sensor. According to the datasheet, it provides an output voltage between 0.5VDC to 4.5VDC. It can display a pressure between 0 Bar to 1 Bar. A measured value of 0.5V corresponds to 0 Bar, an output signal of 4.5V means a pressure of 1 Bar. There is a straight line between these points, each measured baseline value stands for its own pressure value. The measuring instrument thus displays the pressure by measuring the voltage and recalculating it. By interpreting the values and, for example, comparing them to an alarm limit, the measuring instrument becomes a pressure gauge. The sensor could also have measured a different value, for example ammonia, and could have taken the measurements with the same logic.

Analog sensors require power. Depending on the situation and type of sensor, this needs to be continuous or only periodic. Mobeye has focused on powering and reading sensors, even with extremely low energy consumption. This makes the entire measuring setup suitable for battery-powered operation or powered by solar panels.

Resistance measurement

Many temperature sensors work by changing the electrical resistance of a metal or semiconductor through temperature. The measured temperature is derived from the change in resistance. Examples are PT100 and PT1000 sensors.

Pulse generator

A pulse generator is readable via a pulse counter. For example, flow meters usually consist of a (water) wheel. As water flows through a tube, the wheel will turn and periodically give a pulse which means it closes a magnetic contact. If the water flows faster, the wheel will spin faster. Each turn then stands for, for example, 10 liters of water.

What can Mobeye do for you?
Mobeye is a manufacturer of measurement, log, control and reporting technology. Several Mobeye products are delivered including a sensor. Most Mobeye products can read potential-free sensors. For reading out analog sensors and pulse generators, Mobeye offers the “analog products”, such as the Mobeye SISTM and Mobeye CML4055. These read out analog sensors, convert the values to a meaningful unit, and log them in a graph or tabular form, in addition to monitoring alarm limits. Unique is that Mobeye products and the sensors also work battery powered, for situations where no external voltage is available

Do you want to read a remote sensor, receive notifications or get insight into the values?
Consult Mobeye for more information.