Dwyer DLI - Manual (Page 91)

91 | P a g e
Transmitter Output Modes
Real-time data transmissions may be sent through the RF antenna, the device’s serial port, both or
neither. If both the serial and RF transmitters are disabled, the device will function strictly as a
standard data logger. The typical user will configure the device for wireless transmission only thus
transmitting data from the device to the RFC101A receiver. However, serial transmission may be
desirable for some systems where the built-in transmitter is not powerful enough to maintain a
reliable link, the signal must be brought outside of an environment that blocks RF, or when a
hardwired connection to an alternate transmitter is required. Additionally, both modes may be
enabled for combined local and long-distance monitoring of the signal. See “Increasing Range with
the RFExtender” later in this manual.
Transmitter Options
The transmitter module has four configuration options. Two of these options pertain to enabling and
disabling the transmitter under different operating conditions and two pertain to the timing and
format of the transmitted signal. These options are summarized below.
1. Transmit only while logging – If this option is selected, the transmitter will only output data
when the logger is recording data to memory. When memory is filled and the device stops logging,
the transmitter will stop as well to indicate the logger needs to be offloaded and restarted. If the
memory wrap-around mode of the logger is enabled, the device will continue to overwrite the oldest
internal data and continue transmitting data wirelessly. If this transmitter option is not selected, the
transmitter will continue to operate regardless of whether the device is recording data.
2. Transmit under switch control – If this option is selected, the on/off switch may be used to
inhibit the transmitter output. This allows the user to manually stop the transmitter without affecting
the logger operation or transmission timing. This may be useful for transporting the device through
an area where other devices are operating on the same frequency band, disabling the transmitter until
the device is placed in-system, or disabling individual devices to evaluate system performance and
troubleshoot interference or collisions. In systems where a manual override is not desirable, this
option may be left unchecked, and the transmitter will not be affected by the position of the switch.
NOTE:The above two transmitter options function as such: if either one of the modes would disable the transmitter
under given conditions, the transmitter will be disabled. For the transmitter to be enabled, the required conditions
must be met for both options to allow the transmission.
3. Randomize transmit interval – If this option is selected, the transmitter will wait a short random
delay of up to 5 seconds before it transmits each data packet. This can decrease the chances of lost
packets due to devices "talking over" each other because of long-term timer drift. Devices that are
initially synchronized to transmit 10 seconds apart can drift in their timekeeping by up to 2 seconds
per day, meaning that they could potentially interfere with each other after a few days of sustained
operation. Because the transmission lasts less than a second, a random delay of up to 5 seconds can
allow the majority of the transmissions to escape interference. If this transmitter option is not
selected, the device will transmit at the interval set by its timer to within a few milliseconds. It is then
up to the user to make any necessary accommodations for the timer drift. See Using Multiple
Devices later in this manual.
4. Use error correction – If this option is selected, the transmitter output format will be modified to
include a simple forward error correction scheme known as a Hamming code. This method of error
correction allows the receiver in a one-way transmission to correct any single bit error in each block
of eight data bits being received. This option may help to increase system reliability in some
environments.
NOTE: System reliability will most commonly be degraded by loss of signal or by burst noise longer than a single
bit, thus this option may not substantially improve performance for the typical user. Additionally, if this option is not
selected, the device may be able to transmit two complete copies of the data packet, increasing the likelihood that