LCR Meter: The UNI-T UT603 (Review)

A few weeks ago we reviewed the DE-5000 LCR meter. This time, let’s take a look at the UT603 from UNI-T. Like the former, it’s also made to measure inductance, capacitance and resistance of electronic components.

Overview

The LCR meter, encased in a robust plastic body, has dimensions of 172 x 83 x 38 mm. This size is comparable to many handheld multimeters, including the UT61D that I personally use. There's a family resemblance with other products of the same brand, with the bright red rubber cover, the dark gray body and the blue and yellow buttons. It feels quite sturdy, the red protective cover fits snugly around the meter. 
  The UT603 is equipped with an LCD which is large and clear. The 22mm-high digits are easy to read, and the display is 3 ½ digits, or 2000 counts. The measured value is displayed on a single line.

Besides L, C and R values, this meter also measures the forward voltage of diode junctions and the gain of bipolar junction transistors. Finally, there’s also a continuity mode with a buzzer, as is the case on many multimeters. The UT603 however isn’t a multimeter, and there is a helpful “Do not test voltage” warning on the front, that will hopefully prevent any confusion. It is worth noting that the meter is entirely manual; each range has its own position on the rotary switch. 

The meter is powered by an included 9 V battery. Besides the meter and the battery, the package also contains two short banana-to-crocodile test leads and a short user manual.    

Uses for the UT603

Measuring capacitors can be an important aspect of equipment troubleshooting and repair. However, there are plenty of multimeters that already include a mode to measure capacitors. So, how is the UT603 different then? The main difference is that many multimeters measure capacitance by charging the capacitor under test with a known current and measuring the time required for a given increase in voltage at its terminals. This method can lead to incorrect results if the capacitor has both lost part of its capacitance due to aging and developed a significant series resistance (ESR). The ESR will slow down the charging, and the multimeter will interpret that as a higher capacitance than is actually the case.
  On the other hand, the UT603 is measuring capacitance with an AC signal and measures the phase shift introduced by the capacitor. Thus, it will give a measurement potentially closer to reality than would a multimeter. It can be used as a complement if you already own a multimeter and maybe an ESR meter. This is useful in the repair of a wide range of equipment, including power supplies, vintage electronics like old radio receivers, test equipment, and larger machines with electric motors that need start or run capacitors. 

One of the main benefits of a tool such as the UT603 is the ability to measure inductance while being affordable. This is beneficial if you are self-studying electronics and you'd like a tool for practical experiments with inductors (LC, RLC circuits, oscillators, filters, transformers, etc). The inductance measurement mode also allows to check motor windings, contactor coils, etc.

Operating Modes

The UT603 has five different operating modes:

• Inductance (L)
• Capacitance (C)
• Resistance (R)
• Diode mode/continuity beeper (combined mode)
• Measurement of transistor gain

The L mode has five separate ranges that must be chosen manually on the rotary switch, from 20 H (that’s a lot!) to 2 mH. The resolution on the smallest range is 0.001 mH, or 1 µH.
  Similarly, the C mode is divided in seven ranges, from 2 nF to 600 µF. The resolution on the smallest range is 0.001 nF, or 1 pF. On the other hand, I found 600 µF to be a bit on the low side, as it’s common to see 1000 µF or 2200 µF capacitors in consumer equipment and switch-mode power supplies.

Finally, the R mode has six ranges from 200 Ω to 20 MΩ. The transistor gain measurement will be, in most cases, rarely used and doesn’t need any particular comment. The continuity (beeper) mode works as expected. When continuity is established between the probes, it’s very slow to start beeping, but when it’s beeping, it will make a screeching noise if the connection is not perfect. Hence it can be used to hunt for bad connections in connectors and cables, by listening to whether or not the buzzer sound is continuous.

Here is a summary of all the ranges available and the corresponding rated accuracies.
 

Using the UT603

When you switch on the device, you'll notice a little peculiarity, not very common these days: the On/Off button is latching, and will stay down once pushed. I admit it's not particularly spectacular, but it's worth noting in this world where everything has membrane keypads and soft tactile switches. As a consequence, it will stay on until you turn it off; there is no auto-power off on the UT603.

There is another switch of that type, labeled L/C. This is rather confusing: although you can select the L or C range you want on the rotary switch, you also have to remember to select the desired L or C mode using the L/C push switch. This is a bit cumbersome, but it's possible to get used to it. If you forget to press the L/C switch, and the function L (or C) selected on the rotary switch, the position of the L/C switch and the component you are measuring do not correspond, you will obtain either a negative value (which immediately tells you something is wrong) or a “1” on the left of the display, meaning “out of range”.

Once the instrument is powered on and a range is selected on the rotary switch, the component under test can be connected. Through-hole components with long leads fit directly into the slots marked “-||- / Lx” just above the (+) banana socket. The polarity doesn’t matter, even for electrolytic capacitors, because the test signal is AC anyway, and its amplitude is very low. Components with shorter leads that don’t work well with the built-in slots, or larger components can be connected using the supplied banana to crocodile clips, allowing a maximum distance between clips of up to about 30cm. It’s not so easy to measure surface-mount components, as no SMD tweezers are supplied. However, custom cables could be quite easily made in a DIY fashion. 

Just like many LCR meters, the UT603 can be damaged by charged capacitors. Remember to discharge them fully using an appropriate resistor before measuring them. 
  One last thing to remember is to turn it off once you’ve finished using it. Otherwise, it will happily stay on until the battery is flat. On that topic, I’ve measured that the “low battery” indicator on the LCD turns on when the battery level drops to 5.9 V. This is good: there are six 1.5 V elements in a 9 V battery, and that figure means that the UT603 is able to use the battery completely, down to less than 1 V per element, when some other tools start complaining when the “9 V” battery drops to 8 V. The instrument draws about 14.5 mA in the L and C modes, and about 6.2 mA in R and other modes. Taking the higher consumption of the two, that's still about 35 hours of continuous use with a fresh 9 V battery.

Who Is It For?

The UT603 LCR meter can be a relevant tool for students, enthusiasts and hobbyists on a tight budget, seeking an affordable way to experiment with inductors. For example, building custom filters, oscillators, cross-over networks for home-made speakers, etc. Those who work with motor windings and large inductors (up to 20 H) will find it useful too. However, it's important to note that the UT603 is not a one-size-fits-all instrument. It lacks ESR measurement capabilities and has limited ranges, making it less suitable for very small or large values of inductance and capacitance.
 

Strengths of the UT603

I liked in particular:

• The clear and easily readable screen.
• The battery usage. It doesn't waste energy and uses the batteries to their full capacity.
• Its affordable price point.
• In most measuring ranges, the UT603 provided values that matched my other instruments, with an error margin of just a few percent, as promised by the manufacturer.
• Comes with a good tilting stand: the instrument is stable on the bench.

I liked less:

• The fully manual operation. It needs a lot of interaction with the rotary switch and L/C switch; an automatic mode would be more comfortable.
• The build quality may feel slightly plasticky, particularly the protective rubber jacket, which tends more towards a plastic texture than rubber. 
• The measuring ranges are limited compared to other instruments, which are admittedly much more expensive.

 

Going Further

In conclusion, the UT603 LCR meter is a solid option for those needing basic functionalities at a lower cost. It offers a clear screen, straightforward measurements with accuracy in line with the manufacturer's specifications in most ranges, and efficient battery use, appealing especially to students and hobbyists. However, it has a few drawbacks, such as limited measuring ranges and some quirks in the user interface. For those considering other options, the UT612 (also from UNI-T) or DE-5000 could be alternatives, though it's worth noting that the cheaper UT612 is still about three times the price of the UT603. This price difference makes the UT603 a more viable choice for budget-conscious users who need essential inductance measuring capabilities.