Electrical measurements of non-electrical quantities

Electrical measurements have great accuracy, reliability, simplicity and cheapness. Therefore, electrical measuring instruments are widely used in measuring also non-electrical quantities.

The electrical system measuring non-electrical quantities includes the main components, such as: a sensor (converter), intermediate devices and an indicator.

Electrical measurements of non-electrical quantities are essentially conversion by a sensor of a non-electrical quantity, say, a change in the liquid level, speed of movement, temperature, etc., into a change in the electrical quantities: resistance, voltage or current, measured by an indicator that is a simple electrical instrument.

Instruments used for electrical measurements are divided into two categories:

• Analog ("teshki") - in them the measurement result on the scale of the device shows the arrow;

• Digital - in them an analog-to-digital converter converts the input signal to digital and outputs its value to the LCD.

Today, digital devices have replaced analog, we can say completely, because, first of all:

• They are easy to use (unlike analog (arrow), they do not have concepts such as measurement limits or calibration of the scale of the device in which it is necessary to understand);

• They are much more accurate than analog ones.

One should note the following advantage of such devices: electrical measurements allow testing non-electric values even in hard-to-reach places or at a considerable distance.

Consider two specific examples of how to conduct electrical measurements using devices that measure non-electrical quantities.

Moisture meter for wood

Since wood is a hygroscopic material, with changing environmental parameters, its humidity changes - one of those properties of wood that are so important when used in finished products. Therefore, the wood is dried to a uniform state, taking into account future operating conditions.

One of the methods for measuring its humidity is the use of electric moisture meters . The principle of the moisture meter is to measure humidity, which is based on electrical properties. Using the device, you can quickly determine it without destroying the wood.

Hydrometers are of two types:

• Needle - based on their measurement of electrical resistance;

• Capacitive (non-contact) - they are based on the relationship between the permittivity and humidity. These moisture meters have sensors that do not require the introduction of needles into the wood. Therefore, there are no traces left on the surface of the wood after the measurements, which, of course, distinguishes them in this respect from needle hygrometers.

Meter of nitrates

Nitrates are one of those chemical compounds that are most dangerous, since they can cause serious disturbances in the human body. Once ingested in large quantities in the human body, they can cause nitrate poisoning, various chronic diseases and disorders.

A time-consuming and expensive process for the detection of nitrates is currently carried out by a small special device - the nitrate meter.

Nitrate meters are designed to measure in fruits, vegetables and fresh meats containing nitrates. Their work is based on the measurement of ion activity by the electrode system using a direct potentiometric method, the results of which are converted into an electrical signal proportional to the concentration of NO3 ions.

To determine and measure nitrates by piercing the product, a special probe (probe) is provided in the device.

The nitrate meter is a digital device. Its measurements are displayed on a convenient color display.