Thermometer for gas water heater. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Thermometer for gas water heater. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Power regulators, thermometers, heat stabilizers

Comments on the article

The use of a gas water heater (column) installed in some apartments is often associated with inconvenience. If, for example, the column is located in the kitchen, then to check and adjust the temperature of the water filling the bath, you have to repeatedly go from the bathroom to the kitchen and back. It is advisable to install a water temperature sensor at the place of its consumption, and an indicator next to the column. In this case, you can adjust the temperature without leaving the column.

An electronic thermometer, the circuit of which is shown in fig. 1 solves this problem. The temperature sensor is three semiconductor diodes connected in series (VD1-VD3). They can be of any type - germanium or silicon. It is only important that the diodes are small-sized, this will reduce the inertia of the device. A stabilized supply voltage of 5 V is supplied from any suitable source. The consumed current does not exceed 10 mA. I used the BP2-3 power supply from the BZ-34 calculator kit.

Thermometer for gas water heater
Fig. 1

The operation of the thermometer is based on the fact that the voltage drop across a semiconductor diode at a constant forward current depends linearly on the temperature of its p-n junction. If, at zero temperature, the engine of the tuning resistor R5 is set in such a way that the voltage between it and the minus of the power source is equal to the voltage drop across the diodes VD1-VD3, there is no current through the PA1 microammeter under these conditions. With the heating of the diodes, the voltage across them decreases and a current proportional to the temperature will flow through the microammeter.

The frame of the microammeter used by the author with the resistance Rp=617 Ohm is made of copper wire (temperature coefficient of resistance a=4.3*10^-3 ° C^-1). When the temperature of the frame changes by dT=20 °C, the increase in its resistance will be

dR \u617d Rp * a dT \u4,3d XNUMX * XNUMX^-3*20=53 ohm

Since the dynamic resistance of the diodes VD1-VD3 is small and the values of the resistors R4-R6 are small, the current flowing through the RA1 microammeter at a given temperature depends mainly on the sum of the resistances R2, R3 and Rp. In this case, it is approximately equal to 7 kOhm. Having made the proportion 7000 Ohm - 100%, 53 Ohm - x%, we find

X=53*100/7000=0.76%

Consequently, with temperature fluctuations at the installation site of the RA1 microammeter by 20 ° C, the thermometer readings will change by less than 1%. But if you leave one diode in the circuit, in order to maintain the same sensitivity of the device, you will have to reduce the total resistance of the resistors and the frame by three times, so the error will triple.

The thermometer is calibrated in the following sequence:

by immersing the VD1-VD3 diodes in a vessel with melting ice (snow), the trimming resistor R5 sets the pointer of the RA1 microammeter to the zero mark of the scale;
immersing the diodes in a vessel with boiling water, set the arrow to 3 ° C with a trimming resistor R100.

It remains to fix the diodes on the pipe through which hot water flows, as close as possible to the place where you want to control its temperature. A possible mounting option is shown in Fig. 2.

Thermometer for gas water heater
Fig. 2

So that the temperature of the diodes 2 does not differ from the temperature of the pipe 1 and the water in it, the assembly should be covered with asbestos thermal insulation 3, and on top of it - with aluminum foil 4. With wires 5, the length of which is practically unlimited, the diodes 2 are connected to the rest of the thermometer elements that can be placed near the geyser regulator, even located in another room.

Author: V.Burkov, Ivanovo

See other articles Section Power regulators, thermometers, heat stabilizers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

truck x-ray 07.06.2000

At US customs, the installation of new X-ray machines has begun, which work not on X-ray transmission, but on their reflection and can view anything - from a living person to a multi-ton truck.

The computer processes data on the energy of X-rays scattered from the object, and builds an image of everything that is inside a suitcase or truck: hidden weapons, drugs, explosives, illegal passengers. On the new device, just in case, every XNUMXth passenger arriving at US international airports is scanned.

The dose of radiation received in this case is not more than the dose of cosmic rays per minute of flight in an airplane at an altitude of 10 kilometers.

Other interesting news:

▪ Android M OS will double the battery life of smartphones

▪ CD 500 TB

▪ Mobile supercomputer from NVidia

▪ Volitronics Success

▪ How a laser cuts flesh

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Civil radio communications. Article selection

▪ article Serpent-tempter. Popular expression

▪ article In what continent was the special cult status of people of the third sex spread? Detailed answer

▪ article Car batteries. Directory

▪ article Electronose warmer for the treatment of the common cold. Encyclopedia of radio electronics and electrical engineering

▪ article RF sound probe. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews