User's Manual

About the A740
1 Introduction
This manual explains the hardware aspects of Adcon’s A740 addNODE Remote
Telemetry Unit, including installation issues and certain parameter configurations.
The manual is divided as follows:
• "Introduction", which gives some general information and document
conventions.
• "Using the A740 RTU", which details the installation and use of the remote
telemetry unit.
• "Performing Advanced Functions", which discusses technical information
for the advanced user.
• "Specifications", which describes operating parameters for the devices.
1.1 About the A740
The A740 addNODE Remote Telemetry Unit (RTU) is a portable low-power,
medium-range telemetry device capable of sampling up to 8 analog and 4 digital
inputs. The analog inputs offer a resolution of 14bit (13bit+Signbit). The digital
inputs can be used as fast (up to 10 kHz) or slow (<10Hz) counters or frequency
measuring inputs.
Furthermore 4 protected digital low-side switches and one analog (0-2.5V, 10Bit)
output are available. The digital outputs can be used in conjunction with the PWM
capabilities of the CPU.
A V24/RS232 serial interface is also built in, allowing for configuration, firmware
upgrade or communication. An SDI-12 interface, capable of supplying 5.5-
7V/100mA sensor power, is available on the A740, but is not yet operational. The
SDI-12 functionality will be included into the firmware of the A740 soon.
The A740 RTUs incorporate an A431 radio module operating in the 430 to 470
MHz range, making it adaptable to most radio communication regulations in the
world. The output power is variable up to 0.5 W, while the modulation is narrow-
band FM (6.25, 12.5 or 25 kHz channel spacing).
Due to its construction, as well as to the software controlling it, the power
consumption is extremely low. The RTUs operate from a built-in NiCd 6.2 Volt
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