GPS channels
GPS channels are sourced from the GPS connector on a SomatXR module. EGPS-200, EGPS-200-Plus and Garmin GPS modules are supported.
The Garmin GPS (model GPS18X-5Hz) module requires the 5 Vdc power option and draws about 0.5 W. EGPS-200 and EGPS-200-Plus modules require the 12 Vdc power option and draw about 2.4 W. On boot up of the SomatXR, the power is always set to 5 Vdc.
With the power option set to 5 Vdc, the EGPS-200 and EGPS-200-Plus modules operate in a minimal mode that is sufficient to send a message to the SomatXR processor allowing it to identify the module. When the SomatXR receives this message, it switches to the 12 Vdc power mode.
CAUTION
The Garmin module will be instantly destroyed if it is connected to the GPS connector with the 12 Vdc power option selected! As such, always power off the SomatXR before connecting a Garmin GPS if an EGPS-200 or EGPS-200-Plus module was previously connected.
All GPS modules source standard NMEA sentences that provide GPS fix position, fix quality, fix date and time and other standard navigational parameters.
NOTE
Position accuracy varies with several factors including, but not limited to, GPS receiver configuration, location (geographic latitude, as it influences HDOP, and surrounding objects possibly blocking reception or causing multi-path reception), satellite constellation status and ionosphere conditions.
- The Garmin GPS module also sources dilution of precision parameters (i.e., positional, horizontal and vertical). All Garmin channels are sourced at 5 Hz.
- Both the EGPS-200 and EGPS-200-Plus modules source proprietary NMEA sentences that provide IMU information (i.e., tri-axial acceleration and vehicle yaw rate, roll rate and pitch rate). Both also provide a high accuracy 3D Speed computed channel. All of these channels are sourced at 200 Hz.
- The EGPS-200-Plus module additionally sources real time kinematic (RTK) parameters (i.e., yaw and pitch) using two antennae that must by properly and accurately mounted on the vehicle. These additional channels are sourced at 20 Hz.
All modules provide GPS PPS time sync pulses that allow the SomatXR to align the GPS channel data to be synchronized in phase with other SomatXR channels (i.e., analog and digital input channels).
Note that this “PPS sync” can only be achieved when the GPS module is providing fix date and time information. This will not be immediately available when the GPS module is first connected to the SomatXR, or after the SomatXR module is power cycled, or if the vehicle loses GPS satellite reception for any other reason. The time required for the “PPS sync” to become active is in part module type dependent, but can vary from a few seconds to well over one minute. The system provides a “pps_sync_active” channel; this is a logical channel that is true (1) when the “PPS sync” is active and false (0) when it is not active.
The SomatXR supports a GPS raw message channel that captures all of the NMEA sentences received from the GPS module. The timestamps for the messages are the times when the messages were received – not the “PPS sync” adjusted times.
Generic parameters
- Connection: A unique hardware identifier created by the system.
- Reading: Current value of the channel. Show the readings by selecting the desired channels and clicking
Live update. Not in edit dialog.
- Units: The reading unit description shows in this column.
- Name: The channel name must be unique and contain valid characters (invalid characters are single and double quotes, '\', '@', '#', '&', '<' and '>'). Invalid channel names are 'true' and 'false' (case sensitive).
- Description: Enter an optional detailed description of the channel.
- Collect: Select the Collect checkbox to write the channel data to the SIE data file during a test run.
- Chart type: Set the default chart type for the channel. Not in edit dialog.
- Decimals: Set the default decimal places for channel displays.
- Sample rate: Set the desired channel sample rate. If the sample rate changes, all dependent computed channels and DataModes™ are changed automatically.
- Speed mode: For MX411B-R Highly Dynamic Universal Module channels, select Normal or High for the channel speed mode. To successfully run a test, this channel parameter should match the module speed mode.
- Measurand: Enter an optional measurement type.
- Data type: The format of the channel data output (read only).
- Expiration time: Specify the time period in seconds that can elapse without data before data is considered stale and the output is set to the invalid value. The value may be any real number greater than zero.
- Invalid value: Specify the value to be set when the expiration time has elapsed without any data. The value may be any real number.
Scaling parameters
- Scaling mode: Set the channel scaling mode.
- Defined slope intercept: Specify the Slope and Intercept of the scaling line.
- Defined zero span: Specify the Electrical zero of the sensor scaling line. Enter both the Electrical span and the Physical span.
- Defined two point: Specify the Electrical 1, Physical 1, Electrical 2 and Physical 2 points to define the scaling line.
- Experimental two point: Use the Experimental two point scaling option to define the two point parameters based on experimental measurements.
- Electrical units: Electrical units of channel input.
- Units: Physical units of measurement for the channel.
- Electrical 1: Specify for Defined two point scaling mode. Automatically set after Experimental two point scaling.
- Physical 1: Specify for Defined two point scaling mode. Automatically set after Experimental two point scaling.
- Electrical 2: Specify for Defined two point scaling mode. Automatically set after Experimental two point scaling.
- Physical 2: Specify for Defined two point scaling mode. Automatically set after Experimental two point scaling.
- Electrical zero: Specify for Defined zero span scaling mode.
- Electrical span: Specify for Defined zero span scaling mode.
- Physical span: Specify for Defined zero span scaling mode.
- Slope: Specify for Defined slope intercept scaling mode.
- Intercept: Specify for Defined slope intercept scaling mode.
- Prerun zero mode: Set to Interactive only to allow channel zeroing.
- Prerun zero offset: Automatically set after zeroing a channel.
- Prerun zero target: Specify before zeroing a channel.
- Range min and max: Specify the expected extreme values of the channel. Values may be set as positive or negative numbers.
- Warning and Alarm min and max: Specify the desired values for warning and alarm thresholds.