The Max186 is an 12 bit 8 Channel ADC. Eight Channels means it can measure 8 different voltages at once. There are many sensor around today that output a voltage and to take the reading from them you need to measure a voltage. Analog to Digital converters are a way to interface the Basic Stamp to the analog world. They can measure hundreds of volts depending on the voltage divider you use. The reason for a voltage divider is because the MAX186 ADC can only take an input voltage of 4.096V. A voltage divider a way the divide the voltage you want to monitor. For instance say you want to monitor a 12V car battery. But the MAX186 can only handle 4V right. So how would you do this? Simple, a voltage divider. To measure 12 Volts you want to divide the voltage by 3. So all you need it a 220K resistor and a 100K. Put them in series and connect your 12V to the 220K and GND to the other end of the 100K. Then your output to the Op-amp comes from the middle where the two resistor are connected. Here is a forumla to firgure out the output. Vout=(R2/RT)*Vin Now put the 12V into the formula Vout = (100K/320K)*12V= 3.75V Now just times the 3.75V by 3.2 in your stamp program to get 12 Volts. If you want to measure 100V, for instance, use a 1M and and a 33K.

Now here is what the op amp is for. The opamp is in a voltage follower configuration. This is a special case of a noninverting amplifier where all of Vout is fed back to the inverting input. The straight feedback connection causes a voltage gain of appx one and a Av (Current gain) of one. The most important feature of the voltage follower are its very high imput inpedance and its very low output inpedance. These features make it a ideal buffer amplifer for interfacing high impedance sources and low impedance loads. In other words it isolates the Input from the ADC. Another feature of the opamp is its noise filtering. The two inputs of the opamp go directly into a differential ampifiler which compares the inputs and cuts the nosie out completely. Most of todays sensor that put out voltage are very senitive (such as the LM35) which puts out 10mV/degree C and if you have the slightest bit of noise and your readings are going to be off by quite a bit. If you want more detailed info on the MAX186 download the data sheet. Also the Max186 is available from Maxim for free. Go to the products section and click request free samples and they will send them to you.