Operation Of The Hmr3000 In Detail; Pc Demo Z Reference Calibration Method - Honeywell HMR3000 User Manual

HMR3000 User's Guide
5. If sufficient tilt change were not encountered during the calibration procedure, then the calculated Zoffset value may not
be reliable. In such a case the Z offset would likely will appear in red, and the corresponding check box empty. User has
the option to accept this Z offset value by checking the box.
At the end of each calibration, PC DEMO software calculates and reports a variation number as a sign of magnetic
environment change/goodness; the lower the number the better the calibration. The compass should be relocated if the
variation number is greater than 40.

2.11.3 PC DEMO Z Reference Calibration Method

In applications which changing the tilt of the host is not possible, an approximate value of the Zoffset can be found by
using the Z Reference Method. This method directly compares the Z component of the earth's magnetic field in an
undisturbed location to that of the host. This procedure involves two steps:
Step 1. Collect Z reference value near the calibration site, away from large metal objects that will distort the earth's field
by:
1 Select the Diagnostics menu, and then select Capture/Clear Z Reference.
2. Hit Read Data, and hold the compass approximately level.
3. Hit the Stop button after capturing 10-20 readings, and hit the Apply New button to save the new Z Reference value in
the EEPROM of HMR3000.
Step 2. Install the compass on the vehicle/mount and follow the normal 3D Calibration described above in 2.11.2. Mag Z
offset will be computed from the Z Reference method as well as the normal method.
1. At the end of the calibration, between the Stop and Apply button selections, ensure the MagZ check box is un-checked,
and the Z Reference check box is checked.
2. Select the Apply button to save the new offset values.

3.0 OPERATION OF THE HMR3000 IN DETAIL

3.1 GENERAL
The HMR3000 digital compass consists of three magnetoresistive magnetic sensors, and a liquid filled two-axis tilt sensor
to produce tilt compensated heading data. A microprocessor controls the measurement sequence of the sensors, and all
the parameters that control the operation are stored in an EEPROM. The output sentences of the HMR3000 conform to
the NMEA 0813 standard for Marine communication (NMEA = National Marine Electronics Association).
The HMR3000 has four operational modes:
Continuous Mode
Output unsolicited NMEA standard message(s) at a configurable rate
Strobe Mode
Active Strobe Mode- Measurement is continuous and message output on request
Passive Strobe Mode- Measurement and output upon request
Sleep Mode (requires an interrupt signal at the connector)
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