Emerson 396RVP instruction manual Compensation Elements

MODEL 396R pH/ORP	SECTION 6.0
	MAINTENANCE

4.Following the caution above, wash the glass bulb in dilute 5% hydrochloric acid solution and then rinse it thoroughly in tap water. Replace the sen- sor if it cannot be cleaned. If the glass bulb appears clean, proceed to step 5.

5.Buffer calibrate the sensor (Refer to Section 5.0). If the sensor appears to respond sluggishly to pH change, soaking it overnight in a weak acid solution (5% hydrochloric acid) may improve its response. Be sure to follow the CAUTION above and to rinse the sensor’s tip thoroughly with tap water. If the sensor will not calibrate, it must be replaced.

6.4Cleaning Platinum Electrode. The electrode is never exposed to these undesirable compounds. In the event poisoning is suspected, the electrode can be restored to normal operation by simply cleaning the plat- inum electrode with baking soda. Polish it by rubbing it with a damp paper towel and baking soda until a bright, shiny appearance is attained.

6.5Automatic Temperature Compensator. The tem- perature compensator element is temperature sensi- tive and can be checked with an ohmmeter. Resistance increases with temperature.

The 3K element will read 3000 ohms ± 1% at 25°C (77°F) and a Pt-100 will read 110 ohms. Resistance varies with temperature for a 3K and Pt-100 element and can be determined according to Table 6-2 or the following formula:

RT=Ro [l+R1 (T-20)]

Where RT = Resistance

T = Temperature in °C

Refer to Table 6-1 for Ro and R1 values:

TABLE 6-1

Ro and R1 VALUES FOR TEMPERATURE

COMPENSATION ELEMENTS

Temperature	Ro	R1
Compensation Element
3K	2934	.0045
PT-100	107.7	.00385

TABLE 6-2

TEMPERATURE vs RESISTANCE OF AUTO

T.C. ELEMENTS

	Resistance
Temperature °C	(Ohms) ±1%
	3K	PT-100
0	2670	100.0
10	2802	103.8
20	2934	107.7
25	3000	109.6
30	3066	111.5
40	3198	115.4
50	3330	119.2
60	3462	123.1
70	3594	126.9
80	3726	130.8
90	3858	134.6
100	3990	138.5

6.6Sensor Tube Replacement When Used With A Sensor Head Junction Box. Replacement of the retraction versions sensor tube assembly involves the removal and installation of two sets of male connectors: One at the process end of the sensor, and the other at the junction box end (See Figures 6-1,6-2). Refer to Section 6.2 for proper removal of the sensor from process.

1.Remove sensor from process before proceeding. The junction box with attached male connector must be recovered from the old sensor for reuse. Unscrew the junction box cover and set aside. Disconnect electrical connections from printed cir- cuit board inside junction box. Disconnect BNC connector to preamp. Unscrew hex nut (D) from male connector body (C). Separate junction box from used sensor. Set aside.

2.Pry off split ferrule from sensor and set aside for reuse. Remove hex nut (D) and set aside for reuse. Check that the internal O-ring is in place in the male connector body (C) attached to the junc- tion box.

3.Remove hex nut (B) from male connector body (A) at process end of sensor and set aside. Slide the Teflon ferrule and the male connector off sensor in the direction of junction box and set

NOTE

If stainless steel ferrule was used, male connector body (A) will have to be dis- carded with the sensor tube.

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