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eTrac TiltTrac (US Digital A2 A2T A4 HBA2 HBA4 HD25A) - 03


The TiltTrac by eTrac is a rugged waterproof inclinometer, suitable for the positioning of, for example, crane arms and dredge heads. This driver outputs the measured angle from 0 to 360 degrees and has a resolution of 0.1 degrees, since the accuracy of the unit is also 0.1 degrees.

The sensors are 'daisy-chained', which means that the sensors are connected to each other in a chain, which simplifies installation. One chain is connected to one COM port. Up to 15 units can be connected in one chain.

The zero-point of any sensor can be set with the software provided with the units and is remembered after power-down.

The interior of the unit contains a US Digital absolute encoder. Since the communications protocol for several of US Digitals encoders is identical, this driver can also be used for the following types of absolute encoders: A2A2TA4HBA2HBA4HD25A.

Driver Information

Driver US Digital A2/A2T/A4/HBA2/HBA4/HD25A  Interface Type Serial  Driver Class Type Counted
UTC Driver (question)  No Input / Output Input  Executable DrvQPSCounted.exe TILTTRAC ACTIVE 
Related Systems
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System Configuration

The software supplied with the sensor is called SEI Explorer. All settings should be correct by default, but the software is useful for checking this and determining the addresses of the different sensors. When the tool is opened, its user interface should look something like the screenshot below:

Make sure that the resolution is set to 3600 and all optional options are disabled.

Database Setup

The absolute encoder can be used as a Pitch Roll Heave Sensor and as a Rotation Angle Sensor. The encoder that is built in the eTrac TiltTrac is a Pitch Roll Heave sensor.

In Database Setup, add a Pitch Roll Heave Sensor to your setup en select the eTrac TiltTrac driver. To use the encoder to measure relative angles, add a Rotation Angle Sensor to your setup and select the U.S. Digital driver.

Select the COM port you have connected a chain of sensors to. The following settings apply: 9600 baud rate, 8 data bits, 1 stop bit, no parity. These should be the default settings.

Note that it is possible to set the TiltTrac to a different baud rate with the supplied software, but this setting is not remembered when the sensors are shut-down. Therefore, we strongly recommend using the default baud rate.

In the same dialog, also set the maximum update rate. It is recommended to set this to 0.1 seconds, which is 10 Hz. The maximum update rate at the default baud rate is around 20 Hz. To use this, leave the maximum update rate field at 0 seconds. Again, we recommend 10 Hz, since going any higher than that would not significantly improve accuracy and only put a strain on your system due to heavy COM port usage.

Usage as Pitch Roll Heave Sensor

Click Next to go to the next page in the setup wizard. Leave all rotation measurements and conventions settings at their default values. Any misalignment can be corrected here.

It is important to note the "Slot number" field. Since the sensor only measures one angle, Qinsy must be told which angle that is. It must also be told which address to use. To this end, either a 'P' or 'R' (for pitch and roll, respectively) must be entered in the slot ID (slot number) field, followed by a hexadecimal character which represents the address number. To define a pitch and a roll in one system (so two sensors on the same object), simply add another 'P' or 'R' and its address number.

To refresh: a hexadecimal character is 0-9 for 0-9 and A-E for 10-14. Example: address 13 is character 'D'. You can check the addresses in the software supplied with the sensors.

Some examples:

P0: sensor with address 0 used as pitch.

RA: sensor with address 10 used as roll.

P1R2: sensor with address 1 used as pitch, sensor with address 2 used as roll.

Usage as Rotation Angle Sensor

Click Next and add an observation of the type Rotation (X), Rotation (Y) or Rotation (Z). These represent the axis around which the sensor rotates.

This sensor needs a slot ID to identify it on the communication bus. Use the software that is supplied with the sensors to determine the correct address. The slot ID is the address number, in hexadecimal representation.
To refresh: a hexadecimal character is 0-9 for 0-9 and A-E for 10-14. Example: address 13 is character 'D'.

Make sure that all systems connected in one daisy chain have the same settings: COM port, baud rate, update rate, etc. Except of course the slot ID, this should be different for every sensor.


In the Observation Physics display, the raw sensor angles can be seen. Note that the sensors output an angle between 0 and 360 degrees. When used as pitch or roll, Qinsy will convert these angles from -180 to 180. For example: 355 degrees is used as -5 degrees in Qinsy.

Since the sensor also sends some status information, this is also decoded and can be seen in the quality indicator (QI) field of the raw data. See the table below for the interpretation of these values.

Meaning quality indicator values

QI value



no error


not enough light


too much light

-3 to -5

misalignment or dust


hardware problem


fast mode error


multiturn pos. not initialized


checksum failure

When values -1 to -6 are seen, something is probably wrong with the sensor. Values -7 and -8 occur when non-default settings are used (fast mode and multiturn mode; the sensors should be in single-turn mode). When frequent checksum failures occur, check the cabling and pay attention to EMI (Electro Magnetic Interference).

Note that if you want to disable the checksum, add NOCS in the file (can be found in your Qinsy installation directory) to the command line parameters of this driver.

Also note that if one of the sensors does not respond, the driver will wait for it to respond, so a drop in update rate can be observed.