Electronic Measuring Instruments Selection Guide
Electronic measuring instruments cover LCR meters and function and signal generators; for an LCR meter, test frequency and measured parameters decide.
This guide explains what to check when selecting products in the Electronic Measuring Instruments category.
LCR and capacitance meters
LCR and capacitance meters apply an alternating test signal to the component, and the measured value depends on the frequency of this signal. The first data to check is therefore the test frequency: the product data lists steps of 100 Hz, 120 Hz, 1 kHz, 10 kHz and, on some models, 100 kHz. Measuring a component at the frequency at which its value is given in the datasheet makes comparison meaningful.
- Measured parameters. Besides L, C, R and Z, the dissipation factor (D), quality factor (Q), phase angle (θ) and equivalent series resistance (ESR); on some models, DC resistance (DCR).
- Equivalent circuit. The device calculates a lossy component with a series or parallel model; the product data states that either mode can be selected.
- Construction. Battery-powered handheld models are for service and field work; the benchtop model can be connected to sorting setups on a production line through its RS-232 and Handler interfaces.
The data for basic models such as the UT601 and UT603 does not include test frequency selection or ESR. If you only need to see the capacitance value, digital multimeters with a capacitance range are in a separate category.
Function and signal generators
Function and signal generators produce ready-made waveforms such as sine, square, ramp, pulse and noise, as well as arbitrary waveforms defined by the user.
- Frequency. The headline value is the upper limit of the sine output; the limit is lower for other waveforms. For a model giving 120 MHz on sine, the data states 30 MHz for square and pulse and 5 MHz for ramp. Look at the row for the waveform you need.
- Channel count. There are single- and dual-channel models; choose two channels when two signals with a phase difference, or a signal together with a trigger, are required.
- Sampling rate and vertical resolution. These determine the time and amplitude detail of an arbitrary waveform; the data includes rates such as 125 MSa/s and 500 MSa/s and 14-bit and 16-bit resolution.
- Modulation and operating modes. Modulations such as AM, FM, PM and FSK, and sweep and burst modes, are listed in the model data. Sweep mode makes it easier to plot the frequency response of a filter or amplifier.
- Output impedance. Given as 50 Ω (typical) in the product data. The output amplitude varies with the load: in the data, the upper amplitude limit is written as 10 Vpp into a 50 Ω load and 20 Vpp into a high-impedance load. The load setting on the device must match the connected circuit.
To view the generated signal, you can look at the oscilloscopes category.
Micro-ohmmeters
Micro-ohmmeters measure very low resistances such as contacts, busbar joints, windings and cables. In a four-wire (Kelvin) connection, the current and voltage leads are separate; this way the resistance of the test leads and contact points does not enter the result. In the data, look at the resolution (1 µΩ or 10 µΩ), the test current by range, the memory and the upper/lower limit alarm. Battery-powered portable models are used in the field, and models with RS232, RS485, LAN and Handler interfaces are used in production testing. For battery and cell internal resistance there are separate cell and battery testers.
DC electronic load devices
Electronic load devices test sources such as power supplies, batteries and solar cells with an adjustable load; they mostly convert the energy they draw into heat. Constant current, constant voltage, constant power and constant resistance are the common operating modes.
Three limits must be satisfied together when selecting: load voltage, load current and total power. Power is often the deciding one: if a load rated 150 V and 30 A is limited to 150 W, it can draw 30 A only up to 5 V. For dynamic tests, the current rate of change and dynamic frequency are compared, and for automation the RS232 or RS485 interface. For the supply side of the test setup, see the laboratory power supplies category.
Brand and order notes
- In Unit model codes, the UTG prefix indicates generators and the UTL prefix indicates electronic loads; you can use the model code (for example UTG2082B) in the search.
- Products are sold by the piece.
- Most products in this group are listed as made-to-order; the lead time is confirmed before ordering.
Comparison and selection table
| Selection Criterion | Digital Multimeter (DMM) | Digital Clamp Meter | Insulation / Earth / Phase Sequence Tester |
|---|---|---|---|
| Primary Function | AC/DC voltage, resistance, continuity, diode, mA | Non-intrusive AC/DC current measurement via jaw | Insulation resistance (MΩ), earth ground or phase rotation |
| Key Technical Spec | True RMS, auto-ranging, display resolution | Jaw opening (mm), current range (400 A – 1000 A) | Selectable test voltage (250 V / 500 V / 1000 V DC) |
| Safety Rating | CAT III 600 V / CAT IV 300 V | CAT III 600 V / CAT III 1000 V | IEC 61557 compliance & CAT III / CAT IV rating |
| Typical Application | Control circuit troubleshooting & bench testing | Live motor feeders, PFC banks & distribution cables | Commissioning, preventive maintenance & audits |
Frequently asked questions
What is the difference between an LCR meter and the capacitance range of a multimeter?
A multimeter only shows the capacitance value, and the test condition cannot be selected. An LCR meter applies an alternating signal to the component at a selectable frequency; besides capacitance, inductance and resistance, it also gives the dissipation factor (D), quality factor (Q) and equivalent series resistance (ESR). If you need to measure a coil, evaluate component quality or verify a value at a specific frequency, choose an LCR meter.
What is ESR and why is it measured?
ESR (equivalent series resistance) is the loss resistance that behaves as if it were connected in series with the capacitor's ideal capacitance. As its value rises, the capacitor heats up more under ripple current and its filtering function weakens. For this reason, in power supply repair, capacitors whose capacitance looks normal but whose ESR has risen are looked for. LCR meters give the ESR value at the selected test frequency.
Are a function generator and a signal generator the same device?
In everyday use the two names are interchangeable; they are also used together in the product names in this category. In the narrow sense, a function generator produces different waveforms such as sine, square, triangle and sawtooth. High-frequency RF signal generators, on the other hand, usually give only a pure or modulated sine. When selecting, look at the waveform list and frequency range, not the name.
Why is four-wire (Kelvin) measurement needed?
In a two-wire measurement, the resistance of the test leads and contact points is added to the result; at the milliohm level, this addition can be larger than the measured value itself. In the four-wire method, one pair of leads carries the current and the other pair takes the voltage directly across the part being measured. Because almost no current flows through the voltage leads, lead and contact resistance do not enter the measurement.
What tests is an electronic load used for?
In power supply, battery, solar and fuel cell, and generator tests, it loads the source in an adjustable way. In constant current mode, the source's voltage behavior under load and its current limit are examined; in constant resistance or constant power mode, a real load condition; and in battery testing, the discharge behavior. In dynamic mode, the load current is changed rapidly to observe the source's transient response.