Automotive voltmeter with an accuracy of 0,1 volts. Free Technical Library article

Free technical library

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

Automotive voltmeter with an accuracy of 0,1 volts

Free technical library

Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices

Comments on the article

The possibility of premature failure of an expensive battery forces the motorist to carefully monitor the operation of the voltage regulator relay and the state of the vehicle's on-board electrical network. The voltage in it should not differ by more than ± 3% from the optimal value, which is determined for the given operating conditions of the battery and depends on the climatic zone, the location of the battery and its technical condition, and the mode of operation of the vehicle. The more precisely the optimal voltage is maintained when recharging the battery, the longer it will last.

The correct operation of the car generator is of great importance. With an increase in the generator voltage above the optimum by 10-12% (about 0,15 V), the service life of the battery and electric lamps is reduced by 2-2,5 times.

In order to accurately perform all the necessary adjustments, you need a special voltmeter that measures voltage in the range of 13-15 V with an accuracy of 0,1 V. It is difficult to buy such a device, but many will be able to make a similar one with a scale stretched in the range of 10-15 V. Increased measurement accuracy, a linear scale over the entire measurement range, the absence of its own power source, increased reliability (due to the protection elements provided in the device that do not affect measurement accuracy), the ability to adjust the "stretch" zone of the scale are the distinguishing features of this device. It is made on the basis of an operational amplifier and is a voltage difference meter.

Specifications of the voltmeter

Automotive voltmeter with an accuracy of 0,1 volts

Ris.1

The voltmeter is powered directly from the measurement object. The initial offset relative to which the measurement is made is set by the resistance of the chain of resistors R3, R4 (see the circuit diagram in Fig. 1), and the feedback value (which determines the gain of the OUDA1 and, accordingly, the degree of "stretching" of the range) is set by the resistance of the chain of resistors R5, R6.

The reference voltage source on the zener diode VD3 also provides a potential shift at the non-inverting input DA by an amount equal to approximately half of the measured voltage drop, which is necessary for the operation of the op-amp with a unipolar supply.

The resistance of the resistor R7 depends on the sensitivity of the microammeter RA and the maximum output voltage of the operational amplifier relative to the cathode of the zener diode VD3.

Diodes VD1, VD2 protect the op-amp, and VD4, VD5 protect the microammeter from overcurrent. VD1 prohibits the passage of negative current through the resistor R1 and the operational amplifier. It is possible to pass current through a zener diode VD3, biased in the forward direction, a diode VD2 and resistors R2-R4. Thus, a potential difference of not more than 3,2 V will be established between the DA inputs (pins 0,7). A similar voltage drop will be at pin 3 relative to pin 4 of the op-amp.

This ensures reliable protection of the op amp from errors when connecting the polarity.

The voltmeter uses fixed resistors of the MLT type, it is desirable to use multi-turn types SP5-2, SP5-3, SP5-14 as tuned resistors. It is permissible to use other types of op amps, for example, K140UD7 or K140UD1A, K553UD1 with the appropriate correction circuits. Diodes - any low-power silicon. The KS147A zener diode can be replaced with a KS156A, but, probably, then the temperature stability of the voltmeter will deteriorate and it will be necessary to clarify the values of the resistors R1-R3. Microammeter - M906 or M24 with a total deflection current of 50 μA and a scale corresponding to the selected measurement zone. It is also possible to use other pointer devices with a total deflection current of up to 1 mA, but in this case it is necessary to select the value of the resistor R5, based on the selected value of the voltage drop across it (about 1,5 V). You can also use the avometer in microammeter mode. Then this device will be made in the form of a prefix to the tester.

In the absence of defective elements and installation errors, the adjustment of the voltmeter is reduced to its calibration. This operation is performed using an adjustable power supply with an output voltage of 9-16 V and an exemplary voltmeter, preferably digital, for example B7-16, FZO, BP-11.

Trimmer resistors are set to the middle position and a voltage of 12-13 V is applied to the input of the voltmeter, controlling it using a standard instrument. The pointer of the adjusted voltmeter should deviate from zero. Then, a voltage of 10 V (± 0,05 V) is set at the output of the power source, and the voltmeter needle is set to zero division of the scale with resistor R4. Then, by increasing the measured voltage to 15 ± 0,05 V, the arrow is set to the final division of the scale with resistor R6. By repeating these operations for 10 V and 15 V, they achieve the most accurate setting of the voltmeter in the operating range of 13-14,5 V.

During the establishment of the relay-regulator, the voltage is measured directly at the battery terminals.

Figure 2 shows a printed circuit board with a layout of elements. The board is installed on the contact bolts of the M906 microammeter and placed with it in the box.

Fig. 2

Author: V. Bakanov, E. Kachanov, Chernivtsi, Modeler-Constructor No. 12, 1990, p. 27; Publication: cxem.net

See other articles Section Automobile. Electronic devices

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Memory on moving nanotubes 26.01.2009

The founder of nanotechnology, Eric Drexler, believed that nanocomputers would use mechanical rather than electrical elements. A project led by scientists from the University of Nottingen, led by Dr. Elena Bichutskaya, allows us to get closer to this dream. And the goal of this project is to create permanent computer memory on two-layer nanotubes.

A thin, shorter nanotube is inserted into a thick nanotube fixed on an electrode. When an electrical signal is applied, the thin nanotube moves out of the thick one, reaches the second electrode, closes the circuit, and remains in this position, held by van der Waals forces. A new signal can return the handset to its original state.

It turns out that each such pair is one bit, which is either 0 or 1, and the recording density, taking into account the angstrom diameters of nanotubes, turns out to be colossal. The main problem is to make such double tubes in sufficient quantity and evenly fix them on the electrode.

News feed of science and technology, new electronics

We recommend downloading in our Free technical library:

▪ site section Indicators, sensors, detectors

▪ radioscheme magazines (annual archives)

▪ book Voltage transformers and their secondary circuits. Vavin V.N., 1977

▪ article Why did one pilot land the plane twice right next to New York bars? Detailed answer

▪ article Lacquer for tin. Simple recipes and tips

▪ article Peat electrical installations. Protection. Encyclopedia of radio electronics and electrical engineering

▪ reference Entering the foreign TV service mode. Book #10

Leave your comment on this article:

All languages of this page

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