Comparison UNI-T UT890C vs UNI-T UT890D

The parameters that the device can measure.

— Tension. Voltage (potential difference between two points in a circuit), measured in volts. One of the basic electrical parameters, supported by all types of devices, except for oscilloscopes (see "Device"). Parallel connection is used for measurement. In analogue instruments (see "Type") voltage measurement can be carried out without power.

— Current. The strength of the current flowing through a certain section of the circuit; measured in amperes. There are two ways to measure current strength: traditional and non-contact. The first one is available in almost all devices with the ammeter function, for this it is necessary to open the circuit and connect the device to the gap in series (moreover, with the analogue principle of operation, the ammeter does not require power). The second method is used in current clamps (see "Device"). In most cases, the models are able to measure direct and alternating current.

— Impedance. Impedance of a certain element to direct electric current; measured in ohms. Note that in this case we are talking about traditional measurements that are not associated with ultra-high resistances characteristic of insulation (in insulation, this parameter is checked using a separate method, see more about it below...). Impedance measurements are carried out as follows: a certain voltage (low, within a few volts) is applied to the probes of the device, after which they are applied to the place of measurement — and the impedance of the tested section of the circuit or other object is calculated from the strength of the current flowing through the formed circuit. Thus, to operate in ohmmeter mode, a power source is required — even for an analogue instrument.

— Capacity. The capacitance of a capacitor is measured in farads (usually microfarads and other derived units). The measurement itself is carried out by supplying an alternating current to the capacitor. This function can be useful both for clarifying the capacitance of unmarked capacitors (initially unmarked or with erased inscriptions), and for checking the quality of signed parts. On capacitors, in addition to the nominal capacity, the maximum deviation from the nominal value may be indicated; if the measurement results are outside the tolerance limits, then it is better not to use the part. If the deviation is not indicated, then it can be assumed that it should be less than 10% of the nominal value. For example, for a 0.5 uF part, the range of allowable capacitances will be 0.45 – 0.55 uF.

— Temperature. Temperature measurement — usually, using an external remote sensor, usually on a probe. In electrical engineering, this function is used to control the operation of parts that are sensitive to overheating or that must operate in a certain temperature regime.

— Frequency. The ability to measure the frequency of an electrical signal is primarily characteristic of oscilloscopes and scopometers, but it can also be found in other types of devices — the same multimeters (see "Device"). This, usually, implies the ability to display specific numbers corresponding to the frequency in hertz.

— Duty cycle. Duty cycle is one of the basic characteristics of a uniform pulse signal, namely the ratio of its repetition period to the duration of a single pulse. For example, if each 2 ms pulse is followed by a 6 ms pause, then the signal repetition period will be T = 6 + 2 = 8 ms, and the duty cycle will be S = 8/2 = 4. Do not confuse the duty cycle with the duty cycle: although these characteristics describe the same property of the signal, they do it in different ways. The duty cycle is the reciprocal of the duty cycle, the ratio of the pulse length to the repetition period (in our example, it will be equal to 2/8 = 25%). This term is found mainly in English and translated sources, while in east european electrical engineering the term "duty cycle" is adopted.

— Inductance. Inductance is the main operating parameter of any inductor. The ability to measure this parameter is important in light of the fact that specialists and radio amateurs often make coils on their own, and it is extremely difficult, if not impossible, to determine the characteristics of a part without a special device. The principle of measuring inductance is similar to determining the capacitance of a capacitor (see above) — passing an alternating current through the coil and tracking its "response". However, this function is much less common than capacitance measurement.

— Insulation impedance. Insulation impedance of electrical wires to alternating current. Insulation, by definition, has an extremely high impedance, so the traditional way of measuring impedance (at low operating voltage, see above) is not applicable here — the currents would be too weak and it would be impossible to measure them accurately. Therefore, to check insulating materials and other dielectrics, not ohmmeters are used, but special devices — megaohmmeters (or multimeters that support this mode). A distinctive feature of the megohmmeter is a high operating voltage — hundreds or even thousands of volts. For example, to test insulation with an operating voltage of 500 V, the same megger voltage is required, for a 3000 V material, a 1000 V device, etc., the requirements for different types of insulation are described in more detail in special sources. To achieve this voltage, an external high-voltage module may be required, however, many multimeters that support this type of measurement are also capable of independently generating short-term high-voltage pulses from low-voltage power supplies such as AA batteries or PP3 (see "Battery type"). Note that when working with a megohmmeter, you must carefully follow the safety rules — due to the high operating voltage.

— Power. The power of the electric current is determined by two basic parameters — current strength and voltage; roughly speaking, volts must be multiplied by amps, the result obtained will be the power in watts. Thus, theoretically, this parameter can be determined without a special function for measuring power — it is enough to determine the voltage and current strength. However, some measuring instruments have a special mode that allows you to immediately measure both basic parameters and automatically calculate the power based on them — this is more convenient and faster than doing calculations separately. Many of these devices belong to current clamps (see "Device") and the measurement of the current strength when determining the power is carried out in a non-contact way, and the voltage is measured by the classic contact method. There are other design options — for example, an adapter for a socket: an electrical appliance is connected to a socket through such an adapter, and a multimeter takes current and voltage data from the adapter. We also recall that the active (useful) power of the alternating current is not always equal to the full one — with a capacitive and/or inductive load, part of the power (reactive power) is “consumed” by capacitors / coils. You can read more about these parameters in special sources, but here we note that different models of multimeters may have different capabilities for measuring different types of power; These points do not hurt to clarify before buying in advance.

— Phase angle. Measurement of the degree of shift of two electrical signals (or signal parameters) in phase. Specific types and features of such measurements are different, the most popular are two options. The first is to measure the difference between the phases of a three-phase power supply, primarily to assess its overall quality. The second is an assessment of the phase shift between current and voltage that occurs with a reactive (capacitive or inductive) load on an alternating current source; the ratio between active and apparent power (power factor, "cosine phi") directly depends on such a shift.

— Rotation frequency. In this case, most often we are talking about the possibility of measuring the speed of the internal combustion engine. Accordingly, such models usually refer to specialized automotive multimeters. They are designed mainly for diagnostics and testing of engines that do not have electronic ignition systems. To measure, usually, you need to set the multimeter to the number of engine cylinders and connect it to the ignition system (the specific connection method must be specified in the documentation for the car).

Note that this list does not list all, but only the most popular measurements found in modern multimeters and other devices of a similar purpose. In addition to them, the design may provide more specific features — see "Other Dimensions" for more details.

The upper limit of the lower sub-range in which the device can measure alternating current (see "Type of current").

The operating ranges of modern multimeters and other measuring instruments are usually divided into subranges. This is done for accuracy and convenience in measurements: the lower the subrange, the smaller values it covers, the higher the measurement accuracy at low current values. The minimum alternating current describes exactly the lower range, designed for the weakest current values: for example, if the characteristics in this paragraph indicate 500 μA, this means that the lower subrange allows you to measure currents from 0 to 500 μA.

It is worth choosing according to this indicator taking into account the specifics of the planned application: for example, a device with low rates can be useful for delicate work, such as repairing computers or mobile phones, but especially high current sensitivity is not required for servicing household electrical networks.

The type of battery used in the device. Note that the term “battery” in this case refers to all types of autonomous power sources - both rechargeable and disposable. These include: AAA, AA, C, “Krona”, A23, CR2032, etc.

- AA. Classic AA batteries, one of the most popular sizes these days. Available both in the form of disposable cells and in the form of rechargeable batteries; sold almost everywhere. The number of such batteries required to power a multimeter can be from 1 to 8, depending on the features of the device.

- AAA. “Mini-finger” or “little finger” batteries, similar to the AA batteries described above, but having reduced dimensions (and, accordingly, less power and capacity). However, given that many multimeters are also quite compact and their power consumption is low, this option is found in measuring instruments even more often than AA. The number of such elements in this case is usually from 1 to 4.

- “6LR61”. The batteries have a characteristic rectangular shape with a voltage of 9 V and a pair of contacts on one of the ends. High voltage contributes to the accuracy of measurements and allows even quite “gluttonous” models to use only one battery; so this option is quite popular in multimeters. Note that most often “Kronas”...are produced in the form of disposable cells, but if desired, you can also find batteries of this size.

- 6LR61 and AAA. Powered simultaneously from the two types of batteries described above. As a rule, each of these power sources is responsible for its own part of the functionality (for example, AAA for resistance measurements, Krona for testing transistors), and in the absence of one of the sources, only the capabilities directly related to it are unavailable. However, in general, such a combination is not particularly convenient and practical, which is why it is rare.

— Krona and AA. An option completely similar to the “6LR61 + AAA” described above - except that in this case, instead of “pinky” batteries, AA batteries are used. Also not popular.

— C. Cylindrical 1.5-volt elements. Available in two types - accumulators and batteries; similar in length to AA (50 mm), but almost twice as thick - 26 mm instead of 14 mm. As a result, they provide higher capacity and power supply, but due to their large size they are used mainly in advanced desktop devices. Moreover, many of these devices have an insulation test function, and the number of C batteries in them can be from 8 to 12 - this is necessary to create the high voltages used for such testing.

- A23. Cylindrical cells characterized by high voltage - 12 V, despite the fact that the size of such batteries is only 29 mm in length and 10 mm in size. Most often they are disposable batteries. In general, they are poorly distributed, which is why they are used relatively rarely in measuring instruments.

— LR44 / SR44. Miniature 1.5-volt batteries in the form of “tablets” with a size of 11.6 mm and a thickness of 5.4 mm. They are made only for disposable use; At the same time, simple and inexpensive alkaline batteries are marked with the “LR44” index, and more expensive and advanced silver-oxide batteries with the “SR44” index. In multimeters, as a rule, you can use both one and the other. In any case, due to their small size, the power and capacity of all such batteries is small, so they are used mainly in miniature devices - not designed for serious tasks and not having enough space in the case for more solid batteries.

- CR2032. Miniature button batteries with a voltage of 3 V, having a size of 20 mm and a thickness of 3.2 mm. Like LR44 / SR44, they are found mainly in small devices - incl. very miniature, made in the form factor of a pen or even a key fob; however, due to their larger sizes, they provide more advanced power characteristics, which is why they are noticeably more common. CR2032 elements are made only disposable.

— 18650. Removable lithium-ion batteries are cylindrical, 65 mm long and 18 mm in size. With an operating voltage of 3.7 V, they can also have a fairly high capacity. However, for a number of reasons, this option is not popular - it can be found in some advanced devices.

— Branded battery. Batteries created specifically for specific devices (or series of devices) and not related to standard sizes; often made non-removable. Such batteries can have more advanced characteristics than replaceable batteries, and they eliminate additional expenses - you do not need to regularly buy batteries (or a separate battery with a charger), it is enough to charge the existing power source from time to time. On the other hand, when the charge is depleted, such a battery cannot be quickly replaced with a fresh one - the only option is charging, and this requires an outlet and takes time, sometimes quite considerable. As a result, this method of nutrition has not become particularly widespread.