Teledyne 4220 Membrane, Thicknesses, Probe Installation, Precautions Frequency of service

4220 Flow Meter

Section 5 Options and Accessories

4. Place the O-ring on top of the membrane, generally con- forming to the circumference edge of the probe.

5. Place the thumb and index finger from both hands opposite each other on the O-ring at equal distances.

6. Roll the O-ring down over the end of the probe, being care- ful not to touch the membrane where it covers the probe.

7. Trim off excess membrane with scissors or a sharp knife. Check to see that the stainless steel rod (thermistor) pro- truding below the liquid cup is not covered by extra mem- brane.

Note

There must be no bubbles under the membrane and no creases in it for the probe to function correctly.

8. Shake any excess KCl solution from the probe. Reinstall

		the sensor guard. Keep the sensor in a humid environment
		when not in use and between measurements. The plastic
		bottle that was placed over the end of the sensor when it
		was shipped is ideal for this purpose. Place a piece of moist
		tissue inside the bottle, and slide the bottle over the probe.
5.10.3	Membrane	Isco supplies a 2 mil (.002") thick membrane for use with the
	Thicknesses	D.O. probe. This membrane is recommended for long-term moni-
		toring situations only, typical of our users' applications. Use only
		this thickness membrane with D.O. probes connected to Isco flow
		meters. Do not use other thickness of membranes as the 270 D.O.
		module (no longer sold) used with the probe is calibrated only for
		the 2-mil membrane, and cannot be recalibrated in the field. Do
		not use other membrane thicknesses or inaccuracy will result.
		Besides, the thinner membranes are very fragile and difficult to
		install.
5.10.4	Probe Installation	The D.O. probe attaches to a sensor carrier bracket that snaps
		into an Isco mounting ring. Use the specific size mounting ring

for pipes less than 15" in diameter, and the universal mounting ring for pipe sizes greater than 15" diameter. Refer to the instruction sheet supplied with the mounting ring.

Note

When installing the D.O. probe and its sensor carrier bracket, make sure the mounting slots on the sensor carrier are com- pletely pressed into the mating tabs on the ring. The probe relies on a full engagement between tabs and slots for secure mounting. If the slots are loose against the tabs, the probe may be swept away by the force of the stream.

5.10.5Probe Operation and The following factors determine the life of the D.O. probe and the

Precautions frequency of service.

•Membrane life depends on use. Membranes will last longer if installed properly and treated with care during

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