OceanServer Technology OS5000 Series Installation guide
OS5000 Family of Compasses FAQ Document Rev. 1.0
Please also reference the OS5000 family user guide on our download page
Q. What is the standard OS5000 string and can I change it to a different
format ?
A. OceanServer’s standard digital compasses output heading, pitch, roll and
temperature. You can change the displayed parameters such as adding the raw 3 axis
accelerometer and 3 axis magnetic sensor data. There are also several different
compass formats to choose from (Standard Compass String: $C320.5P0.2R-
18.3T19.0*3C)
Q. Is there any way to check the heading accuracy?
A. A precision compass will measure the field very accurately. If you’re near ferrous
metals, DC currents or magnetic devices (motors), etc, the earth’s field will be distorted.
This can cause a large error in heading. You can verify the field distortion by using a
second compass and comparing results to the OS5000 (for example: a low cost
magnetic needle compass is a quick and simple way to see how your equipment shifts
the position of true north).
Q. Should I be concerned about other components in my system in the near
vicinity of the compass?
A. Yes, many components contain ferrous materials. Nickel will commonly be found in
integrated circuit designs. Other components such as batteries, speakers, power
transistors with iron, microphones can all present issues. The compass should be kept a
safe distance from these items. The fields fall off as an inverse square of the distance so
doubling the distance reduces the field strength by ¼.
Q. Can the compass be calibrated indoors in a metal building?
A. For the highest accuracy you should calibrate the compass in its final mounting
outdoors away from cars or metal structures. The compass will learn a hard iron offset
of the steal building if calibrated indoors and will have errors in a clean environment.
Q. What is the impact of metal structures in the field?
A. The compass calibration routine will make corrections for the device in which the
compass is mounted. The earth’s magnetic field will be distorted by magnetic anomalies
that may existed in the outside world such as a steel bridge, building etc. The compass
heading will be impacted by the degree of the distortion while passing by such
stationary structures. This is the case with any digital compass since they can only
measure the earth’s magnetic field, which is present.
Q. Can I add a declination value?
A. Yes, a fixed heading offset can be applied to all heading output data. In most cases
this is used to adjust for local compass deviation in your area. This information can be
found on the web using the World Magnetic Model and you local Latitude, Longitude.
Q. Can I shield my compass against disruptive magnetic fields?
A. In most cases, it is probably not recommended. Shielding material selection should
be carefully chosen to not block the earths magnetic field to the sensor, or placed too
close to the compass when both electric and magnetic field shielding is necessary.
OS5000 compasses do offer both soft and hard iron calibration routines.
Q: What if I put my compass near a receiving or transmitting radio antenna?
A: In most cases, there are no performance issues with the compass, very strong
electric fields should be looked at closely. Precautions should be taken if the electric field
strength gets excessive and impacts the OS5000 module directly.
Q. Will the compass operate at the North and South Poles?
A: No, at the North and South poles, the magnetic field is vertical and gives no
indication of direction. This is the case with all compasses.
Q. How should the compass board be oriented?
A: The factory mounting is always horizontal to the earth’s surface. Additional,
mounting positions will be available on future releases of firmware (contact support for
availability). suppor[email protected]
Q: I want to mount my compass on a moving platform with motors and or
generators in the near vicinity. Will this impact the OS5000 compass?
A: Yes, electric motors usually generate magnetic fields that can disturb the compass.
Shielding motor or generator housings can reduce interference but you should be careful
not to shield the compass from the earth’s magnetic field. Some trial and error maybe
required to locate the compass when mounting near motors.
Q. Can you measure 360 degrees of tilt?
A: Yes. Roll data is measured at +/-180 degrees (full 360 degrees). Pitch angle is +/-
90 degrees. Resolution will decline slightly at 90 degree angles.
Q. What is the sample rate of the compass?
A. The factory default rate is 7MHz (7 samples per second). Users can set the compass
output rate between -50 to +40. Rate is in samples per second and negative are
seconds per sample. .i.e. 20=20 samples/second, -10=10 seconds per sample. A rate of
0 will stop the compass output completely.
Q. When should I calibrate the compass?
A. You should run through the calibration process once the compass is installed in the
device where it will be used and mounted (see the OS5000 family user guide for step by
step instructions). This calibration will be saved going forward. You can always recall
the original factory calibration if required. You should consider recalibrating the
compass in the event a significant design change is made to the device where the
compass is installed.
Q. What if I make a mistake while calibrating the compass?
A. Just start over, it only takes a few minutes (reference the user guide).
Q. How is the compass impacted by applications that have a lot of dynamic
motion such as UAVs?
Most digital compasses use accelerometers to measure the force of gravity to determine
tilt. This measurement is used to calculate an accurate magnetic heading, pitch and roll
data. Accelerometers will provide disturbed data in applications with lots of dynamic
motion (such as UAVs performing banking turns). Such applications will most likely
require sensors that include gyroscopes and not just accelerometers.
Q. Is there anything I can do about vibration that is impacting my compass?
A. Accelerometers are impacted by dynamic motion and vibration. OceanServer digital
compasses have several filters that can be tried to lessen the impact of vibration
(reference the user guide). Applications with lots of vibration are not well suited for
accelerometer based products.
Q. What software programming help is available with the compass?
A. Visit OceanServer’s download page and look at the software programming notes at
the end of the user guide. http://www.ocean-server.com/download.html
Q. How do I know if the compass will fit in my product?
A. The OS5000 family of compasses are all 1” Square. Users can also visit the
OceanServer download page and pull down 3D Models (IGES files) and Mechanical
Drawings. http://www.ocean-server.com/download.html
Q. What metals and other factors should I be concerned with in my device?
A. Non-ferrous metals (not including iron) like aluminum, copper, or brass do not block
the earth’s magnetic fields although currents can flow through them which can impact
compasses. Ferrous metals such as nickel, steel, and iron will distort magnetic fields.
Given that compasses use the earth's magnetic field, ensure the compass has sufficient
distance from ferrous objects that could bend the field. Hard iron issues are typically
cancelled out by the standard calibration, however, digital compasses should not be fully
incased in a ferrous design. Also note; batteries typically contain a magnetic signature
and electric motors generate magnetic fields that will impact compass performance
Q. What is the difference between soft and hard iron distortions?
A. “Soft-iron" effects are caused by un-magnetized ferrous materials in the vicinity of
the OS5000 compass. "Hard-iron" effects are given by magnetized ferrous materials.
Hard-iron effects are typically cancelled out when you calibrate your compass. Soft-iron
effects should be addressed in the design stage, by giving the sensors appropriate
clearance from ferrous content. OS5000 compasses with firmware 1.4 and later have
the option to run a soft iron calibration routine.
Q: I want to make or source my own cables, what is the pin out for my
compass?
A: The pin out and connector information is covered in the user guide. The user guide
can be found on the download page. http://www.ocean-server.com/download.html
Q: Are the magnetic sensor products RoHS compliant?
A: Yes, with some limited acceptations.
Q: My OS5000 compass does not seem to work? How do I determine if the
product is not working or just a setup issue?
A: You should first check that there are no cabling issues and that power is applied. All
compass designs present themselves as serial port devices, the default data settings are
19200bps, 8-bit data with 1- stop bit and ASCII formatted syntax. Compass data can be
viewed in a terminal program such as hyperterm or by using OceanServer’s compass
demo program. Assuming all setting are correct OS5000 compasses send a 7MHz
streaming data string once power is applied. Note the OS5000-US (only) which offers
both USB and Serial requires the installation of a driver for the bridge chip used on the
suggestions.
Customer Support
Related Publications:
For more information on OS5000 Compasses download the hardware user guide (link
below).
http://www.ocean-server.com/download.html
Copyright © 2008 by OceanServer Technology, Inc. All rights reserved
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