High Precision Mode

This Mode is only available for the OndoSense apex HP sensor

The High Precision Mode allows for the measurement of distance changes with a resolution as fine as 1 µm. When this mode is activated, the current distance to the target is stored as the reference distance, serving as the baseline or zero-point. Any subsequent change in distance is measured relative to this reference. If the distance to the target increases, the output values will be positive; if the distance decreases, the output values will be negative.

Common Use Cases for High Precision Mode:

1. Displacement & Drift Measurements Over Time:

   • High Precision Mode can be used to monitor the position of objects over extended periods, such as tracking the temperature drift of equipment.

2. Profile Measurement:

   • This mode is also ideal for measuring the profile of surfaces by moving the object perpendicular to the radar beam. Unlike laser sensors, High Precision Mode can effectively measure the profile of rough surfaces due to the opening angle and the radar spot size over which the distance is averaged.

Setup High Precision Mode

1. Initial Configuration with OndoNet:

   • Activate the High Precision Mode by clicking on the “Switch Mode” button in the Target View

   • Use OndoNet to set your measuring range. Adapt this to your use case to define the smallest possible range.

   • Configure the Amplifiers using AutoGain. The IQ data for a fix target should show oscillations without clipping.

   • Set the time interval for Reset High Precision Mode after a target loss.

   • Select "Maximum Accuracy" as your Profile as it is the first choice for best accuracy. Select “Long range - Slow moving objects” if you have a maximum distance beyond 6 metes.

2. Finalize Setup:

   • Disconnect your ConfigBox and establish the connection via API.

3. Activate High Precision Mode:

   • Download the Application Notes

   • Enable High Precision Mode by setting the corresponding result data selector. To stop High Precision Mode, simply set a different result data selector. For detailed instructions, refer to the Application Notes.

   • For optimum performance and measurement rate in High Precision Mode, ensure that only High Precision Mode is selected (RESULT_DATA_SELECTOR = 512).

Limitations

• The High Precision Mode is optimized for slow movements. When target movement exceeds 50 mm/s, target loss events may occur.

• It is possible to combine the absolute distance measurement in the standard mode with the high-precision measurement. This can be useful to first determine the approximate distance to a target before tracking changes of the distance to that target. At the same time, this does not allow for a more accurate absolute distance measurement than via the standard absolute distance measurement. The initial absolute distance measurement will contain an error of a few hundred micrometers, that cannot be eliminated via the displacement measurement with the High Precision Mode.

• The high-precision mode will measure accurate distances for targets whose orientation towards the sensor stays relatively constant. For significant changes of the angle of the target towards the sensor, the accuracy of the high precision mode will be affected.

The RESET HIGH PRECISION MODE INTERVAL determines the time after which the measurement in High Precision Mode automatically resets following a target loss. This reset adjusts the baseline value to the current distance. Additionally, you can manually reset the measurement at any time by clicking the “Manual Reset” button.

The Hight Precision Mode can not be read out by the current loop or switching outputs. To access the displacement values through the PLC, you need to configure the RS485 connection via the API

Target lost handling

When the high-precision mode is set up (i.e. the correct result data selector is chosen), upon receiving a MEASUREMENT-command, the sensor returns the high precision distance together with a target lost counter. As long as the sensor is capable of “locking” a given target, the target lost counter keeps the same value. More precisely, the measurement data block corresponding to the high-precision data block consists of 6 bytes: Status (1Byte) + Target Lost Counter (1 byte, unsigned 8-bit integer) + high precision distance in µm (4 bytes, signed 32-bit integer).

Reasons for target lost events

There are two scenarios in which a target lost event is identified:

a) The non-high-precision distance between two consecutive measurements exceeds a certain threshold value defined by the parameter HIGH_PRECISION_DISTANCE_THRESHOLD (see section below).

b) The distance to the target changes by more than ~0.6 mm between two consecutive data points.

The former occurs typically when an obstacle interferes in the measurement path between sensor and target or when the target has a smooth surface and gets tilted away from the sensor, so that the signal path is dominated by paths including clutter reflections.

The latter occurs typically when the target moves too fast away or towards the sensor, see below under limitations.

Sensor behavior in case of target lost events

Once a target lost event occurs, the sensor increases the target lost counter by one. (Note: If the maximum value of an unsigned 8-bit integer (255) is reached, the counter resets to zero.) The high-precision data block is now given by a status (TARGET_LOST = -7 (0xF9)), a target lost counter increased by one and a distance value of zero.

For a parametrizable (see below) amount of time, the sensor will remain in this status before it automatically resumes operation of the high-precision mode. Such a resume resets the high-precision distance to 0. When the measurement resumes, the target lost counter does not increase further and does not reset to 0.

Manual restart of the high precision mode

When the sensor is setup for high precision mode (i.e. the result data selector includes the corresponding code (512)), it is possible to manually reset the high precision mode by sending a RESTART_HIGH_PRECISION_MOCE (0x19) command. The sensor will acknowledge the command with an API_SUCCESS (0x01) and set the high-precision distance to 0. Note: The command does not reset the target lost counter. This command also works if the sensor is in a target-lost waiting timer situation. Once the command is received and processed, the high-precision mode resumes immediately.