Honeywell UDA2182 manual Ft of 18 AWG coax

Appendices

15.3Appendix B – Entering Values for Lead Resistance Compensation [Titanium Cells]

(4973 or DL4311 Titanium cells mounted in stainless steel flow chamber 31079198)

Introduction

If you use standard Honeywell cell lead lengths of 7 or 20 feet connected directly to the Analyzer, no compensation for lead resistance is necessary. Similarly, if a junction box is used to extend the leads up to 150 feet, no compensation is required. However, if longer leads are used (greater than 150 feet), signal accuracy can be adversely affected unless you enter information that will permit the UDA2182 to compensate for lead resistance in the black and white cell leads only. Lead resistance compensation is not necessary, nor applied to the other cell leads.

For lengths up to 1000 feet*, simply specify the gauge and length as described in Table 6-5. Note that the maximum wire size for sensor inputs at the input terminal board is 16AWG. Coax cable is recommended for extension of the black and white cell leads.

*DirectLine DL4000 series cells have a total lead length limit of 250 feet.

If mixed wired gauges are used, or lead length or wire gauge are not within the stated ranges, the UDA2182 can still perform the compensation. However, you must first calculate the lead resistance, and then put it in terms of the available settings for AWG gauge and length. Because the smaller gauge coax cables consist of a low resistance shield and a higher resistance conductor, an average equivalent resistance is used for calculations, i.e. 20 AWG wire is used to simulate 22AWG coax.

The resistance of each available gauge choice (in copper wire) is: 16 AWG = 4.0 ohms per 1000 feet

18 AWG = 6.4 ohms per 1000 feet

20 AWG = 10.2 ohms per 1000 feet

(Use 18 AWG values for Input Configuration and calculations)

22 AWG = 16.1 ohms per 1000 feet

(Use 20 AWG values for Input Configuration and calculations)

For example, suppose extension cables between the cell and Analyzer consist of 200 feet of 22-gauge coax and 500 feet of 18-gauge coax. The cell has the TC head option.

500 ft of 18 AWG coax

Analyzer

Junction

Box

200 ft. of 22 AWG coax

Honeywell

Conductivity Cell

Figure 15-2 Example of a Conductivity Loop

202 UDA2182 Universal Dual Analyzer Product Manual January 2009