Describe Physical Environment Monitoring (PEM)/Seismometers here.
Document on how to calculate seismic coherence:
Seismometer Encolsure
We want to stabilize the temperature, pressure, and acoustics, and magnetics near the seismometers to see how it improves the noise.
1. Thermal
- The enclosure should have a high thermal conductivity to eliminate / reduce thermal gradients.
- The enclosure should have a low thermal conductivity to the environment so that the ambient temperature fluctuations are reduced by a lot (how much?)
- There should be temperature sensors on the outside of the foam, the outside of the can but inside the foam, and also on the seismometer itself. What sensors and how much sensitivity?
1. Acoustic
- Reduce the high frequency acoustic noise. It might be making down conversion.
1. Pressure
- The enclosure needs to be nearly airtight so as to keep the pressure on the inside from changing too fast. At 24 hour scales it should track the lab, but not on 1 hour timescales.
1. Magnetic
- We want to shield the seismometer from nearby EMI. Power line harmonics, RFI, and also low frequency EM from motors, etc. This will require using some soft iron, steel, and/or mu-metal.