Unit installation

12-2
RLC-3 V1.80 Copyright © 1998 Link Communications Inc. 9/17/98
The output lines can be turned on and off with Commands 093 and 094. You can recall whether a
line is currently on or off with Command 095. If you want to speak a custom message when you
turn an output on or off, program one of the user macros to speak the message you want, execute
Command 038 (to suppress the rest of the voice responses), and then turn the output line on or off.
Analog Input Lines:
The analog input lines are designed to read a voltage on one of two ranges: 0 to 5 volts, or 0 to 25
volts. You can select which range is used with the DIP switches labeled "Voltage Divider" on the
I/O board itself. If the switch is on, you will be using the 0 to 25 volt scale, because it "divides" the
input voltage by 5. No matter which way the switch is set, most of the discussions about the
analog inputs will speak of the the voltage input as being 0 to 5 volts since the voltage divider is in
hardware and the software doesn't know whether the divider is turned on or not. If you do have
the divider turned on, just remember that 5 volts to the software means 25 volts to you.
The RLC-3 provides a lot of flexibility in how it reads the input lines. Unfortunately, this also
makes things a little bit complicated. Charts have been provided so that you can use the input lines
without understanding how all of the math works, but if you have a unusual application, the RLC-3
can handle that as well. The following paragraphs explain what some of the options are when
reading analog lines. The way you select from those options is described with the commands
themselves.
"Resolution" refers to how many digits after the decimal place you want to know about.
Temperature is usually read to the nearest degree, zero digits after the decimal. When reading a
battery or power supply's voltage, you probably want to hear more than "thirteen volts" or
"fourteen volts", something like "thirteen point six volts". To obtain this kind of reading, you
would specify one digit after the decimal point.
The "conversion ratio" specifies how the controller interprets the voltage it detects. It could also
be called the "scale" or "meter faceplate". If you are measuring wind speed, you may want a
reading that varies from zero to 100 MPH. If wind direction, zero to 360 degrees. If pH, zero to
14. If temperature, way below zero to a hundred degrees or more. No matter what scale you want
the reading to use, the voltage going into the analog line must be between 0 volts and 5 volts (or 0
and 25 with the voltage divider on). If you have a sensor to measure something in the physical
world that can provide a voltage that varies between 0 volts and 5 volts (or 25...), you can set up
the conversion ratio to handle it. The point of this discussion is to make it clear that the controller
does not care what the real-world quantity is, it just needs a variable voltage and the proper
conversion ratio, and it can handle it. You tell the RLC-3 what the conversion ratio is by specifying
two points:
The first is what real world quantity would cause the sensor to output 0 volts. In many
cases this is zero. For example, if you are using a small motor with a propeller to detect
wind speed and the wind is not blowing, you will get 0 volts. But what about temperature?
If our sensor outputs 0 volts for zero degrees, how would we get negative temperature
readings? The analog lines can only accept positive voltages. The answer is that we use a
temperature sensor that outputs about 2.5 volts at zero degrees, less than that when below