Things that Work! Cygnet M-32 Battery Monitor tested by Richard Perez The M-32 is a twelve channel LCD voltmeter and ammeter. It measures DC voltage in six different locations and DC current in six different locations. One M-32 instrument package can monitor any combination of batteries, PV modules, hydros, wind turbines, inverters, and/or DC loads. Instead of many instruments, each with its own display, the M-52 can perform twelve different measurements in a single package. Shipping and Documentation The M-32 arrived via US Post Office in good shape. It was well- packaged in plastic bubble wrap, so I didn't have to spend most of the afternoon chasing styrofoam peanuts around the floor. The documentation is adequate for installation and operation of this instrument. The docs could be much better if they had not been ported over from the sailboat market (the main home of M-32s). The Cygnet M-32 The actual instrument measures 3.2 inches wide by 3.2 inches tall by 2.0 inches deep. It has a six position rotary switch on the front which selects the place of measurement. There is also a two position slide switch on the front that selects either Volts or Amperes measurements. The M-32 uses a four digit LCD numerical display. The display has annunciators for Volts (V) and Amperes (A) as well as + and Ð annunciators. The digits on the LCD display are 0.3 inches tall. The instrument reads voltage to the nearest hundredth of a Volt (0.01 V) from 0 to 32 VDC. Current is measured to the nearest tenth of an Ampere (0.1 A). The rear of the M-32 contains fourteen wire hookup locations for all the various channels. The same model M-32 will work in 12 or 24 Volt systems. The M-32 comes with two shunts for measuring current. The shunt is inserted between the positive pole of the battery and all input and output conductors. These are high quality, 200 Ampere, 50 milliVolt shunts (0.00025 ½) with an accuracy rating of 0.25%. Each shunt contains small fuses for the instrumentation wiring. Extra shunts to fill the additional four current channels are available from Cygnet. The Test System I installed the Cygnet M-32 Battery Monitor in our system at Agate Flat on 13 August 1991 for testing. This system uses a pocket-plate, nickel-cadmium battery for storage. This system is sourced by several PV arrays (Å 60 Amperes at 15 VDC), a wind turbine ( 800 W. peak, or 55 Amperes at 15 VDC), and a homebrew DC engine/alternator (1,500 W. peak or 100 Amperes at 15 VDC). We also use a second nicad battery system sourced by two PV modules strictly to power the radiotelephone. This test system abounds with instrumentation possibilities. Here a diagram of how it will look once I get all the channels connected. INSERT DIAGRAM Test Results Both current (± 1.0% accuracy) and voltage (± 0.2% accuracy) measurements are within Cygnet's specification when compared to Fluke 87 multimeters. The M-32 monitor performs just as its maker says it will. We tested the M-32 in electrically noisy environments and in the presence of RF fields. It still worked accurately. Operating the M-32 Monitor The place of measurement is selected by the rotary switch and the mode of measurement (either Volts or Amps) is selected on the slide switch. All very simple and straight-forward. My only complaint about the M-32 is that I would like to have soft backlighting behind the display for night viewing. As it is now, I have to turn a light on in the room before I can read the meter. Parasitic power consumption of the M-32 was measured at 0.08 amperes or less than 0.1 Watts. Conclusions The Cygnet M-32 Battery monitor comes complete with two shunts for $229. Additional shunts are $24.95 each. The M-32 comes with a two year, repair-replace-or-refund warranty from Cygnet. While two hundred bucks may sound like lotsa money for a digital volt and ammeter, it is very cheap for six voltmeters and six ammeters. And that's what the M-32 really isÐ six digital voltmeters and six digital ammeters sharing a common processor and display. If you bought discrete instruments to make these twelve measurements, then you will spend over six times the money and probably not get the accuracy of the M-32. Real estate in our instrumentation area was getting hard to find. We can only put so many instruments in a finite space. With the use of the M-32, suddenly we have lots of room left over. Access Author: Richard Perez, C/O Home Power, POB 130, Hornbrook, CA 96044 ¥ 916-475-3179. Maker: Cygnet, Inc., POB 4353, Roche Harbor, WA 98250 ¥ 206- 378-5376.