Remote Measurement Systems ADC Data Acquisition and Control

Tested by Chris Greacen and Richard Perez

What is a battery's voltage profile over a number of charge/ discharge cycles? When it's added up, does most of the wind turbine's output come from constant breezes, or the gusts? How much more energy does a tracked module put out, month by month? How do we use power in the course of the day? Precise answers to these questions require loads of measurements, taken at constant intervals, for long periods of time. You could dedicate your days, and those of a few friends, recording measurements like clockwork, armed with a multimeters, clipboards, and superhuman patience. Indeed, this is the way we've collected data for dozens of tests on inverters, charge controllers, and PV modules in past issues.

Data Logger Lust

This is a job for a machine — a data logger — a sort of a super multimeter which records measurements from different sensors into a computer at constant intervals. Here at Home Power we lusted after a data logger for over a year. We looked at units by big companies like Fluke and Hewlett Packard, but found these machines built with too many features (high speed, internal microprocessors and data storage) driving the price up into thousands of dollars. Often the machines were designed for companies like

Boeing, who want to take 10,000 measurements a second on jet engines. We don't need that — we need to take measurements once every few minutes, or every few seconds at most. Besides, none of these machines interfaced gracefully with the Macintosh computer.

The Remote Measurement Systems ADC-1

Imagine our delight when we received, to test, the Remote Measurement Systems ADC-1. It's a 12 bit resolution, ±0.1 mV accuracy data logger, and the bare bones units sells for $489. With some added hardware for appliance control, a power supply and serial cable, a temperature and light sensor, and software to run on the Macintosh, it is packaged as the "EnviroMac", and sells for $899. The ADC-1's 8" x 7" x 2" blue aluminum box has four terminal strips on the front for 16 differential analog inputs, 5 digital inputs, and six controlled outputs. Inside the box, analog to digital (A/D) circuits change the voltages you want to measure into a digital signal for the computer. This signal travels through a RS-232 connector into the computer (on the Mac, it plugs into the modem port). The ADC-1 is powered by a 9 Volt, ac adaptor. It takes 20 mA at 5 Volts, and can run on any DC Voltage from 5 to 18 Volts. A cable from the ADC-1 also runs to a BSR X-10 ac line-carrier remote control system. This plugs into an ac outlet and allows the computer to send signals over your house ac lines to control up to 32 appliances plugged into X-10 modules (you get one module in the EnviroMac package). The ADC-1 also has six controlled 5-Volt TTL outputs. This means it's not just a data-acquisition system — your computer can make decisions based on the data, and turn on and off appliances. For example, you could program your computer to control heating, cooling and airflow in your home, water your garden depending on soil moisture, and work as a security system.

For Macintosh Users

On the second page of the manual it says, "If it takes you longer than 30 minutes [to get the ADC-1 running on your

Current (in Amperes) from each of our four photovoltaic arrays, charted over several hours on 5 February, 1993. Graphed in Excel with data from an ADC-1 data logging file.

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DIY Battery Repair

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