Echelon LonPoint Application and Plug-In - Manual (Page 63)

The LonPoint Application and Plug-in Guide 6-7
Heartbeat Determines how often the functional block sends a
heartbeat over the network. The behavior of the
system in case of a failed heartbeat is determined by
the functional blocks which fail to receive the
heartbeat. Setting this property to 0 disables the
heartbeat for this functional block. Disabling the
heartbeat causes the output network variable to only
be transmitted in response to a changed hardware
input value.
Status
This tab allows you to view and change the status of an Analog Input functional
block. See Status in Chapter 2 for more information.
Analog Input Gain and Current Settings
The analog-to-digital (A/D) converters on the LonPoint module must be properly
configured to match the ADC Settings set in the Analog Input tab of the
plug-in. These can be set via hardware jumpers as described in the LonPoint
Hardware and Installation Guide.
The A/D converters on the module can be programmed for four different input
gains: 1, 2, 32, and 128. The gain settings affect the Ohms, Volts, and Amps
mode settings in different ways, and each will be discussed separately. In
addition, the measurement current for the Ohms setting can be set to one of two
different values.
Amps Measurement Type (2WIR and 4WIR Jumper Settings)
As a rule, the A/D gain should be set to the maximum allowable level so as not to
create an overflow condition. This allows the maximum possible resolution.
Based on the gain setting, the software converts each raw number reading to the
correct value. For current measurement settings (the 2WIR and 4WIR modes),
the gain should be set to 1 for any standard 4-20mA current loop. For example,
a gain of 2 would reduce the maximum allowable current to 12.5mA, which
would not be useful for a 4-20mA current loop.
There are no other software settings associated with the 2WIR or 4WIR settings.
Ohms Measurement Type (RES Jumper Setting)
The resistance measurement setting configures the LonPoint module to measure
the voltage drop from a constant current source through the resistor to be
measured.
There are two resistance measuring current settings: 25µA and 400µA. The
25µA setting is typically used for thermistors, while the 400µA setting is
typically used for RTDs. The determination whether to use the 25µA or 400µA