Geometrics Knowledgebase

Knowledgebase Home | Glossary | Favorites | Contact | Login Knowledgebase Home | Glossary | Favorites | Contact | Login
Search the Knowledgebase Browse by Category
How does Magnetometer noise vary with sample rate?
Article Details

Last Updated
1st of June, 2010

  1. Sensitivity is given as a frequency bandwidth product or nT/rt Hz RMS.  This value is valid for ALL sample frequencies or sample rates.
  2. Sensitivity for the 858 and 859 is 0.008nT/rt Hz RMS
  3. Sensitivity for the 823 and 882 is 0.004nT/rt Hz RMS
  4. Noise levels can also be given as Peak-to-Peak numbers at certain sample rates. For instance at 10 Hz.
     a.      RMS value at 1 Hz for either instrument is approximately equal to the sensitivity
     b.      P-P value at 1 Hz is roughly equal to 3x or 4 x  the RMS value.  Remember that the Root Mean Square is not operating on a sine wave but on some random noise components as well and thus the actual Root Mean Square would be about 0.024nT for the 858 and 0.012 for the 882 at 1 Hz.
     c.      For higher frequencies, we basically take the square root of the sample rate and multiply that times the P-P at 1 Hz.  So for 10 Hz we have 0.075nT for the 858 and 0.036 for the 882.  This is approximately what we see in the field and I can verify that (looking at the noise on an 882 in very quiet area, deepish water, we see less than 0.050nT P-P.)
     d.      So for 20 Hz the multiplier is 4.5 and for 40 Hz the multiplier is 6.3.  So 882 noise at 40 Hz would be 6.3 x 0.012 = .075 nT P-P.
Visitor Comments
No visitor comments posted. Post a comment
Post Comment for "How does Magnetometer noise vary with sample rate?"
To post a comment for this article, simply complete the form below. Fields marked with an asterisk are required.
   Your Name:
   Email Address:
* Your Comment:
* Enter the code below:
Related Articles
No related articles were found.
No attachments were found.

P: (408) 954-0522   ·   F: (408) 954-0902   ·   E:   ·   2190 Fortune Drive   ·   San Jose, CA 95131 U.S.A.