Aplisens SGE-25.SMART User Manual - Page 14

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10.1.2.

Check the „zero point" (SGE-25, SGE-25S, SGE-25C ) bring the probe up above the surface of the

liquid and read the output current. In case of excessive deviation of the zero reading, return the probe to the

manufacturer for adjustment of the conversion curve or adjust the zero point of a device used in conjunction

with the probe (e.g. monitor, regulator, controller).

10.1.3

. Check the „zero point" SGE-25.SMART, SGE-25S.SMART see 10.1.2.

10.2. Additional Inspections.

If the probe is installed in a place where it might have been subject to mechanical damage, wearing cable

covering, excess pressure, hydraulic impulses, sedimentation, crystallization or erosion of the diaphragm, or

excess electrical voltage, inspections should be made as necessary.

Check the state of the diaphragm and cable, clean the diaphragm, check the zero point

10.2.1. Faults in the Transmission Line.

If there is no current in the line or the value of the current is random, check the transmission line, the

connections with the terminal adapters, connectors etc.

If the transmission line is in good order, check whether the probe is functioning correctly.

10.2.2. Effects of Excess Voltage.

In case of a large surge of excess voltage between the wires of the line, the safety diode may sustain damage

due to a low-resistance short circuit (a diode damaged in this way still provides protection to the probe's

circuits).

Symptoms of damage:

- when the probe is connected to the power supply, the value of the current exceeds 20 mA, and the voltage

on the probe is of an order of several hundred mV (in extreme cases a particularly strong surge may cause

circuits or wires inside the probe to burn out; the current is then 0 mA and there is full voltage in the output

circuit).

- when the probe is not connected to a power supply, the resistance of the probe should be measured; this

is approximately 10

Damage to the gas-filled spark gap (Plasma surge arresters) is much less likely than damage to the diode, and

may lead to a short circuit or a lowering of the resistance of the spark gap.

For additional information on how to test the safety devices, see figure. 5a, 5b.

10.2.3. Damage Caused by Overpressure

Another possible reason for malfunctioning of the probe is damage caused by overpressure, which may result

from such factors as

a) freezing of the medium,

b) dynamic effects of a strong current of liquid on the diaphragm seal while the probe is being washed

(applies mainly to the SGE-25S, SGE-25S.SMART model);

c) striking or scraping of the diaphragm with a hard object, such as a screwdriver;

If excess pressure on the probe has caused damage to the silicon or sealing diaphragm, the probe can no

longer be used. Symptoms of such damage are generally such that the output current falls below 4 mA or

rises above 20 mA, and the probe fails to react to input pressure.

10.2.4. Cleaning the Diaphragm Seal

Impurities which have accumulated on the diaphragm during operation should not be removed by mechanical

means such as scraping, scrubbing etc., as this may cause damage. The only permitted method is to dissolve

the impurities, possibly aiding their removal with a light brush.

Sedimentation on the diaphragm may affect the conversion curve.

Examples of ways of cleaning the diaphragms:

In the case of boiler scale on and around the diaphragm, the lower part of the probe including the

diaphragm should be immersed for approximately 20 minutes, for example in a 10% solution of Kamix,

which is available from the manufacturer.

Deposits of petroleum-derived substances should be softened and rinsed off with a solvent of detergent

Deposits of organic substances or food products (juice, syrup etc.) should be softened in warm water up

to 85˚ C, or in detergent in the case of fats.

After removing sedimentation, parts which have come into contact with the solvent substance

should be thoroughly rinsed, and the health and safety regulations relating to the chemical in

question should be adhered to.

Do not use substances which might cause corrosion of the diaphragm seal.

Ω

and is equal to the value of the limiting resistors + resistance of the damaged diode.

DTR.SG...04

(ENG)