Replaced by the LPN-OVP (Rev 1).
The LPN-OVP is reliable and effective in protecting process control equipment against transients induced between the signal lines and instrument earth through lightning strikes or from other sources.
The circuit design is simple but very effective. Gas discharge tubes provide first stage protection, and can discharge up to 5000A when exposed to an 8 x 20msec waveform. Transient voltage suppressors provide the second stage protection, and typically operate within 5nsec, and can discharge 600W when exposed to a 10 x 1000msec waveform.
For maximum protection an LPN-OVP should be used at each end of a field cable to protect process control equipment at both ends.
Note: A close proximity or direct lightning strike may compromise the OVP protection.
Note 1. Each LPN-OVP adds a total of 28Ω to the loop. Two units are recommended for each installation. Eg: 2 units = 2 x 28Ω = 56Ω total loop resistance.
Note 2. Do NOT ground the Signal. Only use the GROUND terminals provided on the LPN-OVP.