Cosa-xentaur Xentaur LPDT Manuel d'utilisateur télécharger pdf (Page 18)

Section 2: Sensor and Sampling Techniques

page 11

Troubleshooting unexpected readings (continued from previous page)

Symptom Diagnostic/Remedy

Reading is not

changing

Condensation will occur if the temperature of the sample system, at any point is below

(colder) the dewpoint temperature of the sample gas. Once having formed, the sample

reaching the sensor will have a dewpoint equal to the temperature of the condensation,

regardless of the dewpoint of the sample at the sample point.

Slow Response

It is usually more satisfactory to bleed a sample gas at atmospheric pressure through

the sensor sampling chamber, and to use 1/8” (3mm) o.d. sample pipe.

See below re: sample pipe material, also see section 2.3

Dry Reading Verify SpanCheck™, or return sensor for full calibration to your representative.

Wet Reading

Cure the leak, or replace unsuitable pipe with copper or stainless steel. Flexible con-

nections should be made with PTFE pipe. NEVER use rubber or plastic pipe.

This type of indicator reads about 10°C dry at about -50°C dewpoint due to tempera-

ture gradients within the device. The error increases at drier levels.

Display Shows

6$7

Dry the sensor, install sensor in either a known dry gas stream i.e. instrument quality

air or dry nitrogen, or place sensor in a dry can or bottle of desiccant and seal the con-

tainer from outside air (the shipping container is designed for this purpose)

Display Shows

6+5

Remove (unscrew) sensor, if the instrument still reads

6+5

the problem is with the

instrument. However, if the instrument reads

231

then check possible cause #2

Remove (unscrew) sensor and note that the meter reading returns to

231

. Use a new

sensor, or apply approximately 20V DC, between the center pin & the filter body of

the sensor, MOMENTARILY with the sensor in a known dry condition. Polarity is not

important, but the contact MUST be very brief or the sensor may be damaged.

Display Shows

Remove (unscrew) the sensor. Short the center contact of the LPDT sensor connection

to the case, if the instrument reads

6+5

the problem is in the sensor, otherwise return

the instrument for service.

231

Check sensor connection or replace sensor.

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Cosa-xentaur Xentaur LPDT Manuel d'utilisateur Page 18

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