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This 6000-count true RMS multimeter has a built-in non-contact voltage detector, low impedance voltage measurement mode and the option of a Bluetooth communication module for wireless data logging. Review by NICHOLAS VINEN Agilent U1233A True RMS DMM with U1117A Bluetooth Adaptor siliconchip.com.au November 2012  71 T he Agilent U1233A Cat III 600V digital multimeter can measure AC and DC volts, frequency, resistance, capacitance, temperature (with a thermocouple), AC and DC amps and microamps and current frequency. It also has diode and continuity test (with a beeper), a display backlight and a built-in LED torch. Additional modes include relative measurements, max/ min measurements, auto or manual ranging, reading hold/ auto-hold and battery state display. There are some things we particularly like about this multimeter. One is that there is no need to change the connections when you switch between amps and microamps modes as there is a single current measurement terminal. Also, the fact that it goes up to 60MΩ in resistance mode is good as many meters will only read to 10MΩ. The bar graph (below the numeric read-out) makes it easier to interpret rapidly changing readings. We also like the probes that are supplied. Not only are they good quality but the probe ends pull off to reveal insulated banana plugs, making it easy to wire the meter up to other test equipment with banana sockets, such as bench supplies. The selector switch is chunky and is logically laid out; they haven’t packed a gazillion different modes into one position. The built-in non-contact voltage detector and torch are nice touches. Also, unlike some meters, it uses four AAA cells for power rather than a 9V battery. 9V batteries are pretty expensive and don’t usually last that long (especially if you’re going to use the LED torch a lot). Features The non-contact voltage detector is called “Vsense” and is located at the top of the meter. When you enable this mode and place that end near a live mains conductor (eg, a wall power point), you get a beeping sound and a red LED lights up. You can set the sensitivity to two levels, high and low. The low-impedance voltage measurement mode is designed to eliminate false readings caused by inductive and capacitive coupling into the wires or circuit you are measuring. This is especially useful in an environment with a lot of mains cables but even in a standard office setting, you can easily get false readings from EMI and hum fields. One interesting feature is the ability to invert the sense of the continuity beeper so that it will beep on an open circuit rather than a short circuit. You can also change the pitch of the beeper. The resolution when measuring capacitance is 1nF, which is higher than we prefer but on the other hand, it will read capacitances over 10,000µF which is pretty good, with a test time of around 10s. We like that it shows you when it is charging and discharging the capacitor under test. Also, the maximum frequency reading is 100kHz which is a little low (some meters will go to 10MHz or more). The basic accuracy of the unit is of the order of ±0.5-1% for most readings with ±2% for capacitance readings, ±1.5% for AC current and ±1.0% for DC current (not including additional lowest digit variation, which is specified in the data sheet). Input impedance for voltage readings is 10MΩ in the normal mode and 3kΩ in the low-impedance mode. The resolution on the lowest range in each case is 0.1mV (volts mode), 0.01µA (microamps mode), 1mA (amps mode), 0.1Ω (resistance mode), 0.001V (diode test/forward voltage) and 0.1°C (thermocouple temperature). Shown larger than life size for clarity, the U1177A Bluetooth adaptor simply clips onto the back of the meter. It has its own battery and on/off switch and communicates with the meter through an optical interface. At the top of the meter, you can see the large lens for the inbuilt LED torch. 72  Silicon Chip siliconchip.com.au The test leads supplied with the Agilent U1233A “feel” much better and more robust than those supplied with most multimeters, while the probes themselves come apart (as shown here) so they can accept other fittings. Bluetooth data logger While this is a nice multimeter, the real reason for us getting a unit to review is the U1177A Bluetooth add-on which clips onto the back. This has its own battery and communicates with the meter via an optical connection. With this add-on, connecting to the meter using Bluetooth is easy. All we had to do in Windows 7 was switch the dongle to “Setup” mode, tell the operating system to add a new hardware device, select the Agilent item which popped up and add the pairing code, which is stated in the provided set-up guide. Then, when the dongle is switched on and in range, the meter appears as a pair of serial ports on the computer. You can then connect to the serial port via a terminal program and read out the value currently displayed on the meter’s screen. Agilent provide free software, called “Agilent GUI Data Logger”, which can be used to log and graph this data at a rate of up to 1Hz. The software can also control some aspects of the meter, such as turning the backlight on and off or changing the data range. While we wouldn’t call this a stellar piece of software, it works OK and we were able to log data from the multimeter into a spreadsheet and a graph. Sufficient information is provided with the U1177A that should you wish to, you can write your own software to interface with it. Note that the U1177A adaptor will work with virtually any Agilent multimeter that has the infrared interface. That includes the majority made in the last few years. By the way, if your computer doesn’t have Bluetooth, you can also get the optional Optical/USB adaptor cable (U1173A) or just buy a USB-Bluetooth adaptor. Conclusion and special offer Currently, Trio Smartcal are offering a free U1177A IR to Bluetooth DMM Adaptor with the purchase of a range of DMMs including the U1230 series. This offer is valid until the end of February 2013. The U1233A True RMS DMM is $164.95 (+GST). The slightly less capable U1231A is $98.95 (+GST) while the U1232A is $141.90 (+GST). We think that’s a pretty good deal, considering the U1233A’s provenance and its range of features, especially when combined with the Bluetooth adaptor. It’s a good basic True RMS DMM with some nice added features and it should provide years of faithful service. For enquiries or purchases, contact Trio on 1300 853 407 or visit http://triosmartcal.com.au SC siliconchip.com.au November 2012  73