Arrow and digital multimeters - advantages and disadvantages

Time is flowing, technology is evolving, and many devices are improving along with them. Newspapers and magazines are increasingly giving way to web pages, cell phones have almost replaced landlines, and no one is using pagers. The modernization and needle multimeters, which are now almost everywhere replaced by convenient digital devices, did not bypass.

The advantages of digital multimeters over analog multimeters are obvious, they have much wider functionality, and their price is not high. So, digital multimeters took their place in the arsenal of not only radio amateurs, but also engineers. Nevertheless, pointer testers are too early to write off, real professionals know that sometimes a pointer device is simply irreplaceable. What is the feature here?

And the difference lies directly in the internal structure of arrow and digital multimeters. The dial gauge, in fact, is an ideal integrator with a large dynamic range and different visual representation of the measurement result.

The dynamic range of the digital device is limited, there is a delay in the measurement and a certain threshold, for this reason the digital device is simply not able to notice some of the types of signals, which means that the user will not notice them either.

The fact is that each digital multimeter contains an ADC and a result processing unit, which initially have limitations on the digitization capacity and processing time of the result for its final display.

The limitation of bit capacity reduces the dynamic range of the device, and the delay associated with processing the result has a completely defined duration, the operation of the device slows down.

Of course, digital devices are constantly being improved, bit capacity is increasing, speed is increasing, response time is shortening, however, a digital multimeter still can not be compared with an analog pointer device.

Dial gauges appeared much earlier than digital ones, and therefore their arrangement is much simpler. The main node here is the electromechanical switch head, it is supplied with electric current through a set of resistive dividers.

Flowing along the turns of a frame placed in a magnetic field and suspended on springs, the current deflects the arrow of the device by a specific angle, reflecting the value of the measured value on a graduated scale in the form of an arc.

The dial gauge contains a set of switched resistors with shunts and a pair of diodes. A digital multimeter has a more complex device, up to the possibility of processing the signal immediately or after measurements, on a computer, but despite the complexity, modern digital multimeters are still not very expensive, since they are mass-produced on the basis of specialized integrated circuits.

Let's look at the advantages that distinguish digital multimeters from analog multimeters, and why digital devices are so popular today.

Accuracy of measurements

The measurement result on the display of the digital tester is visible and understandable for sure, because the meaning of the numbers is known to everyone. In arrow testers, however, there are several scales, you need to look at the scale that you need, depending on the selected range, and calculate the readings on the divisions. The direction of view matters, as well as the position of the device’s body relative to the ground, this is due to the balancing of the frame.

In addition, a constant external magnetic field affects the frame, even Earth's magnetic field has some effect on the readings. Digital multimeters do not have these drawbacks.

Polarity of the measured signal

A digital multimeter does not care what the polarity of the measured signal is, whether it is current or voltage, the minus sign simply appears on the display if the polarity is reversed. The arrow tester will not show the correct value, its arrow will simply lean back towards the limiter and run into it.

Auto Range

Many of today's multimeters can automatically determine the measuring range, and dial meters are often deprived of such an opportunity.

Functional

A digital instrument can do a lot of things that dial gauges cannot, for example measure capacitance, coil inductance, voltage and current frequency, temperature and many other parameters. Some digital instruments are capable of measuring the relationship between measurements, the delta of the measured values, etc. The switch instruments simply do not know how.

Sensitivity and interaction with the measurement object

The digital device is equipped with electronic amplifiers, so it can measure even very weak signals, and practically without affecting the object to which it is connected. At voltage measurement, the digital device has a huge input impedance, and when measuring current, it is minimal. The measurement accuracy remains very high.

Linearity of the scale

When measuring direct voltages and currents, the scale of the dial gauge is linear. If it comes to measuring resistances, or alternating voltages and currents, then an additional non-linear scale is used, and this causes some inconvenience and generates, although small, inaccuracies. In digital devices, this problem does not arise, since there is no dial gauge, and the values ​​are simply read clearly from the display in the form of ready-made numbers.

Gauge zero adjustment

Digital multimeters, as a rule, do not need zero adjustment - neither for an ammeter, nor for a voltmeter, or for an ohmmeter. For switch instruments, zero adjustment is necessary. First, the frame is balanced, the left position of the arrow on the scale, which is built by the adjustment slot located on the front panel of the device.

Even with dial gauges, zero adjustment is necessary for measuring resistances. As the supply battery is discharged and when switching between the measurement limits, the adjustment resistor is set to zero the right position of the ohmmeter arrow.

Influence of battery status on readings

Regardless of how low the power battery is, digital multimeters work exactly. If the battery charge turns out to be critically low, an indicator will appear on the display, which will signal that it is time to replace the battery with a new one, and before that, while the low charge indicator is displayed, the readings will no longer be accurate, and the user will know about it . But until the indicator appears on the display, you can be 100% sure of the accuracy of the readings.

With a pointer multimeter, the situation is somewhat different - the accuracy of the ohmmeter is related to setting the regulating resistor to zero when the probes are closed. As the battery charge decreases, zero floats, and it is important to always remember this and regularly adjust the zero.

It is easier with a digital multimeter - if the indicator lights up, then accuracy is not guaranteed, while there is no low battery indicator on the display, you can be sure of accuracy.

Vibration resistance, resistance to mechanical damage

The design of the gauge frame does not tolerate strong vibrations and impacts. The hairs on which the frame is suspended may break from impact. The digital device is not afraid of shaking, and is much more resistant to shock.

Now let's look at the advantages that pointer testers have over digital multimeters, why they remain indispensable for many years, despite the advent of widely available functional digital devices.

power usage

In the mode of measuring current and voltage, dial multimeters do not usually consume energy from the built-in battery. You can even leave the dial tester in this mode, and not be afraid for the safety of the battery, except that over time it just gets old, as with normal storage. A digital multimeter in the on state always consumes energy; its electronics cannot do otherwise.

For this reason, if you leave the digital device on, its battery will simply be completely discharged. However, in many modern multimeters the function of automatic shutdown is implemented, it will save the battery. Thus, in this aspect, the advantage of dial multimeters is not very significant.

Analog analog tester inertia

Initially, analogue testers are analogous; they do not digitize a signal that requires time; moreover, their arrow mechanism is inertial. For this reason, arrow testers are excellent integrators, they clearly reflect the dynamics of the signal, without wasting time on its digitization.

A digital tester cannot boast of such visibility, there are just numbers on the display - the result of calculations, while the movement of the arrow of an analog device gives an instant idea of ​​what is happening with the measured signal. However, there are combined measuring instruments equipped with both an arrow and a digital display, but these are only rare exceptions.

The main advantage of the pointer devices, supporting their popularity, is the visual dynamics of the arrow.

Susceptibility to interference

The inertia of the pointer device makes it resistant to interference that may be contained in the signal applied to the probes. A digital device will not be able to display readings normally, it will be interfered with, for example, when measuring DC voltage with various kinds of ripples. The pointer device simply averages the measurements, simply integrating them automatically.

The dynamics of the arrow is easily noticeable

Even without looking directly at the dial gauge scale, the movement of its arrow is easily noticeable with lateral vision. This is convenient if the device is on the side and the master is engaged in work; he can, without taking his eyes off the hands, notice a deviation of the arrow without distraction.

Dynamic capacitance measurement

Since the pointer device is an excellent integrator, in the process of charging a capacitor, you can monitor the dynamics of current by the movement of the arrow, this is very convenient, but a digital device will not be able to.

RF field strength

The dial gauge is an excellent indicator of the high-frequency field strength, for example electric field from Tesla transformer not every digital multimeter can handle it, while a pointer device can be safely placed even in a strong field, and thus measure its intensity.

From the above it is easy to understand that both digital and pointer multimeters differ in both advantages and disadvantages, and for each particular case one or another type of device will be convenient. One way or another, it’s good to have both of these types of instruments in your arsenal.

See also on this topic: How to choose a multimeter, How to use a multimeter