Product Number: 7740
Davis Instruments Part Number: 7395-098
Protected Junction Box
Rev. B Manual (7/7/99)
This product complies with the essential protection requirements of the EC EMC
Directive 89/336/EC.
© Davis Instruments Corp, 1997. All rights reserved.
RFI Filtering
The Protected Junction Box includes built-in RFI filtering capabilities. In order
for these capabilities to be most effective, however, you must connect the Pro-
tected Junction Box to an earth ground from terminal JP2. This connection
should use as heavy and as short a wire as possible. The 16.5-foot (5 m) 12AWG
wire provided works well. Connect one end of the ground wire to terminal JP2
and connect the other end to a suitable earth ground. The best earth ground is a
copper rod driven into the earth. Alternatively, you may connect to a grounded
metal cold water pipe.
Be aware that connecting JP2 to ground can cause measurement errors (espe-
cially in temperature) in some cases. To correct the problem, you should isolate
the weather station from any other connections to ground:
✦
Use an ungrounded power adapter for the weather station.
✦
Use a Link Isolator (#7764) to isolate the weather station from the computer’s
ground.
✦
If RFI is not a problem in your installation, you may omit grounding the Protected
Junction Box at terminal JP2.
M
AINTENANCE
I
NSTRUCTIONS
You should periodically look at the surge absorbers to insure that none of them
has “blown” (turned black inside). If an absorber blows you may obtain a
replacement part from Davis or send the Protected Junction Box back for
repairs. Call the service department before returning the Protected Junction
Box. While your Protected Junction Box is being repaired, you may use your
old junction box to keep the weather station operating.
