Pac Lp7-4 Installation

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Gualtar Pennington

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Aug 3, 2024, 5:00:47 PM8/3/24

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Superb Build Quality
Featuring a small footprint high quality casing and removable harness; the LP7-4 converter makes installation easier, especially once you factor in the cable tie tabs on each side.

High Power Handling
The LP7-4 also excels where power handling is involved. Unlike basic passive line out converters and onboard high-level inputs found on mainstream amplifiers the LP7-4 handles up to 55 watts per channel meaning most factory radios can be tapped and incorporated without ado.

Remote Sensing
The LP7-4 also includes an auto turn on remote output feature. Simply supply the interface with constant power and earth and your amplifier can be triggered to turn on once a music source is sensed.

The Teragon LP7 cryogenic level transmitter provides a 4-20 mA current signal proportional to the height of the liquid nitrogen level. The transmitter uses a capacitive probe which is sensitive to the difference in the dielectric constants of liquid and gaseous nitrogen. This capacitive difference is measured and converted to a linear current signal proportional to the level height.

The advanced electronic design of the LP7 results in superior long term accuracy and temperature stability. The 4-20 mA output provides excellent noise immunity, even when transmitting over long lead lengths. The transmitter allows wire runs of over 1000 feet with virtually no signal degradation. The LP7 operates using a simple twisted pair of wires and is readily interfaced to industrial process controllers, monitors and computer systems.The transmitter can be installed on a threaded boss using a tube fitting with an NPT adapter. As an option, the probe can be manufactured with a tube fitting adapter in place. The LP7 comes factory calibrated to your specified sensing length. If desired, the transmitter can be recalibrated in the field using its independent offset and range adjustments.Standard features of the LP7 include:Sensing Lengths from 4 in. to 9.5 ft.True 2-Wire OperationWide Voltage Range (10-30 VDC)Reverse Voltage ProtectedLess than 1% NonlinearityCompact SizeLow CostEasy installation1 Year WarrantyMade in the USAThe LP7 is designed to be a simple, reliable, and economical means of monitoring liquid nitrogen. The LP7 can also be configured to operate with other cryogens and liquids (Ar, H2, CH4, Freons, CO2, LNG, etc.); please call for more information regarding your specific application.

The probe diagram shows the key dimensions of the LP7 transmitter. The probe is a cylindrical capacitor with a vent to allow the liquid to rise between the inner and outer plates. The Sensing Length is defined from the bottom of the probe to the vent. This is the customer-specified length which, when filled with liquid, results in a 20 mA signal. The vent should be located within the liquid nitrogen reservoir. The probe should not be mounted flush against the floor of the reservoir. A minimum clearance of 0.040" (1 mm) is required at the end of the probe to allow the liquid to enter.

The figures below illustrate two typical applications where the LP7 is used to monitor liquid level. The first approach uses a Teragon PM70 Digital Panel Meter which is powered from 115 VAC. The PM70 provides 24VDC excitation for the LP7, measures the LP7 current, subtracts the 4mA offset, scales the result, and then displays it with 7-segment LEDs. In the second approach, the LP7 is powered from 12VDC and the current is displayed with an ammeter. In both of these applications, the LP7 is connected using a simple twisted pair of wires. Normally the case (green) wire is left unconnected.

The LP7 current can also be measured by converting it to a voltage with a resistor as shown below. For proper operation, a minimum of 10 volts is required between the LP7's V+ and V- inputs. This places limits on the resistor value for a given loop voltage, as shown in the graph below. For a full-scale 20 mA signal, the maximum loop resistance is given by:

RMAX = 50 ohms x (VL / volts - 10)
For example, with an excitation of 12 volts, the maximum loop resistance is 100 ohms.

The transmitter can be assembled with a coaxial BNC connector instead of the 3 foot cable. V+ is the central conductor and V- is the outer conductor. Threaded adapters are available in stainless steel with straight or pipe threads. If you require an adapter, please contact Teragon to determine the appropriate Insertion Length. The LP7 can be manufactured to operate with other cryogens and dielectric liquids including argon, hydrogen, methane, freons, LNG, and CO2.

Performing installations in the automotive environment is not only something we love, but also something we are quite good at. The twelve volt automotive environment is both a fascinating and complicated place for high end audiophile grade equipment.

This customer contacted us with a Kenwood KAC-7005PS Five Channel Amplifier and Rockford Fosgate R1-2X10 Loaded Subwoofer Enclosure that they wanted to be installed into their 2012 Honda Civic Hybrid.

We pulled the factory radio and installed the PAC LP7-4 to convert the signal from the stock radio into a useable signal for our new KAC-7005PS! Then we ran the rest of our wiring down to underneath the driver seat where we securely mounted the Amplifier.