RDT 3000 Telemetry Unit
The RDT 3000 is a compact, low-cost, battery powered unit equipped with eight 12-bit analogue
inputs and four digital inputs. It can be configured to read specified inputs at
rates set by switches, and transmits its data using the built-in licence-exempt
433MHz transmitter.
It is ideally suited to expanding the capacity of the Etherlog 3000, which picks up the RDT 3000 transmissions, decodes them, and can process and store them.
It is also capable of operating singly, or as a small network of telemetry units, in conjunction with the host PC transceiver and a PC.
In situations where some sensors must be located a long way from an Etherlog, they can be measured by RDTs, avoiding potentially costly (and electrically noisy) wiring installations. RDT 3000 operating range is up to 200m in the open field, but will depend on the environment (e.g. wall materials) when used in buildings. However, in most cases the range available will be useful in setting up a capable and versatile data logging system.
Input/output capabilities are:
- eight 12-bit unipolar analogue inputs, 2.5V full scale
- four digital inputs
- four 16 bit pulse counters triggered by the digital inputs
Message transmission
The RDT 3000 transmits broadcast messages containing all analogue and digital data at intervals specified by a switch inside the unit. Intervals of 10, 20 and 30 seconds, and 1, 2, 5, 10 and 20 minutes can be selected. Each RDT has assigned to it (at the time of manufacture) a unique identifier, which it sends with the message to indicate the originator. Messages are protected by CRC check codes.Randomised message re-transmit
Since RDT transmissions may sometimes be lost through transmission clashes or noise, the RDT retransmits each message it sends with a randomised delay from the original. The Etherlog 3000 can detect retransmissions and discard them if not required.Message security
The RDT can be configured to send transmissions in an encrypted form, preventing third parties from snooping on the data. The Etherlog decrypts messages as required, using key configuration information held internally. Each RDT has a unique decryption key assigned to it.