LTH Website FAQ’s

We are trying to make things as clear as possible, take a look at our popular FAQ’s below.

Products manufactured by LTH Electronics Ltd are guaranteed against faulty workmanship and materials for a period of three years from the date of despatch, except for finished goods not of LTH manufacture, which are subject to a separate agreement.

All sensors made by LTH Electronics Ltd are thoroughly tested to their published specification before despatch.  As LTH have no control over the conditions in which their sensors are used, no further guarantee is given, although any complaints concerning their operation will be carefully investigated.

Please contact our sales department with the serial number of your product. Our sales department will be able to check our records and confirm if the warranty has expired or not.

Yes we can, we offer an onsite service for planned maintenance, emergency support, installation, on-site commissioning, product training, trouble-shooting or calibration to traceable standards.

Alternatively the product can be returned to our service department at our factory in Luton.

Please contact your local LTH global partner to see if this is possible. Their details can be found on the Global partner’s page on our website. If there is not a global partner listed for your country, please contact our sales department to see how we can help you.

For UK customers we can normally get to site within 48 hours of the request. For non-UK customers please contact your LTH global partner or our sales department to see what we can do.

We can calibrate and service many of our competitor’s products, please contact our sales department with the product details to see if this is possible for your product.

Yes, all our instruments are supplied with an installation / operating manual either as a hard copy or PDF file on CD. We offer an optional pre-configuration service to set your instrument to the parameters required before it is delivered to you simplifying installation and set-up.

We offer training courses for our products. Please contact our sales department for details and costs.

1ms/cm (millisiemen/cm) is equal to 1000µS/cm (microsiemens/cm)

There is no difference. Micromhos is more common in the U.S., while microsiemens is more commonly used in Europe.

Resistivity is simply the reciprocal of conductivity. Generally Resistivity measurements are used in low conductivity or pure water applications.

You will notice that whatever the conductivity of a solution is quoted it is usually referred to a temperature. This is because the conductivity of a solution varies not just with the amount of dissolved salts, but also with temperature. If the conductivity measurement is going to be used to determine for instance the concentration of sulphuric acid it is essential that the temperature effect is eliminated. This is achieved by measuring the solution temperature and compensating the conductivity measurement to the reading that would be given at a standard temperature. This is usually 25°C.

Different solutions will have different coefficients in the order of 1-3 %/°C. The temperature compensation will be quoted in %/°C and to a base temperature. When comparing different conductivity readings on different instruments it is essential that the temperature compensation is performed in the same way. A typical compensation rate of 2%/°C is generally used, but where more accuracy is needed a variable coefficient is essential.

It should also be noted that the conductivity of pure water below 0.1 uS/cm (10M°.cm) has a very large and non-linear temperature dependence. In order to obtain accurate readings in this range of measurement it is essential that the instrument has the correct temperature facilities.

The following maintenance information applies to the conventional electrode type of conductivity cell. The area of the cell that is sensitive to fouling are the electrode surfaces, these must fully “wet” to ensure accurate measurements are made.Moulded cells are often used in applications where a high level of contamination may be expected. This can include contaminates which do not contribute directly to the measured conductivity, e.g. organics, rust and suspended solids, but may form deposits on the electrode surface. In general these may be cleaned with the bristle brush provided and a weak detergent solution mixed with scouring powder.

Problems may occur in hard water areas where the gradual formation of scale will reduce the active area of the electrodes. Simple brush cleaning alone will not remove a hard deposit from the electrode surface. If scaling is suspected the cell should be removed from the system and treated with a 10% solution of hydrochloric or formic acid.The presence of bubbles will indicate that the scale is being dissolved. Cleaning is completed when the bubbles cease and usually takes 2-3 minutes. The cell must be thoroughly rinsed to remove all traces of acid before it is replaced in the system.

Note: Follow the supplier’s data sheet when handling acids and dispose of carefully acccording to your local authority regulations. Cells with stainless steel electrodes are generally used in applications where a low conductivity is combined with a low level of organic contamination and cleaning is rarely necessary. Errors in measurements can often be traced to faulty connections or incorrect setting on the instrument. However if contamination is suspected the cell should be removed from the system and cleaned if necessary.Handling of the cell electrodes will leave residues of oils and greases which will affect the wetting of the surfaces, leading to inaccurate readings. After touching the electrodes wash with a detergent solution and rinse thoroughly. After rinsing check that the surfaces maintain a complete film of water for approximately 10 seconds.

The LTH Electrodeless conductivity instrument and sensor can be calibrated using the appropriate loop resistor(s). Please refer to the appropriate instrument manual or contact our sales department for further details.

LTH Electrodeless conductivity sensors do not require cleaning unless the centre hole through the sensor becomes blocked.

This is a protective cover to prevent the sensor being damaged during transit. This must be removed before the sensor is used.

Yes, the life of the pH electrode will greatly shortened. All pH electrode bulbs should be kept wet at all times.

Never store a pH electrode dry. We would recommend a Potassium Chloride or KCl solution. We recommend any concentration between 2.0 M and 3.8 M. An alternative choice is a pH buffer solution. A pH 4 buffer solution is best since it will keep longer, but pH 7 is also acceptable. Never store the pH electrode in deionised water (DI).

To obtain the most accurate pH measurement, it is important to compensate for temperature. Temperature has two significant effects on pH readings. The solution pH and the electrode output will both change at different temperatures. These two effects, either together or separately, can lead to errors in calibration, measurement and control.

A pH sensor must be mounted at least 15° above the horizontal to consistently function properly. The liquid in the sensor contains small air bubbles. If not inclined slightly above horizontal, a bubble can adhere to the pH bulb where it will affect the sensor’s performance.

This varies depending on a number of factors: Accuracy required, how clean the application is, process operating temperature and pressure. We would normally recommend that you initially calibrate once per week. If you find after a number of weeks the calibration is remaining within tolerance you can then extend the period between calibrations..

1. General: Wash with a solution of liquid detergent and warm water by gently scrubbing with a soft tooth brush or soft tissue. Follow with a thorough rinse in D.I. or tap water.

2. Inorganic Deposits: Try to dissolve the deposit by immersing the electrode bulb in 0.1N Hydrochloric acid for a few minutes followed by a thorough rinse with D.I. or clean tap water. Then proceed with the general cleaning in Step 1 of this section.

3. Organic Oil, Grease Films or Fingerprints: Wash the electrode bulb with the solution in Step 1 of this section. Wash the tip with acetone. Follow with the general cleaning procedure in Step 1 of this section. Note: Depending on the extent of the oil and/or grease contamination, the electrode may be damaged beyond recovery.

4. Plugged or Dry Ceramic Liquid Junction: Try at least one of the previous 3 steps in this section. Place the electrode in KCI solution, 2M or stronger. Heat slowly to 50ºC then let cool to room temperature. Repeat as necessary.

Yes, once the conductivity drops below 50µS/cm problems can be introduced.

Standard pH electrodes contain 3.5M KCl as a reference gel. Samples like DI water and other low ionic solution contain very small amounts of salt. These solutions try to leach ions from the reference gel to raise their conductivity levels. This results in very slow, sluggish, and unstable readings from a conventional pH electrode.

Once you go below this value we recommend using an electrode suitable for Low Ionic strength water and Low Ionic strength buffer solutions.

Our pH electrodes conform to the Nernst Equation for pH output as a function of temperature. At 25°C, the pH output is 59.16 millivolts per pH unit. The electrode will give a zero output at a pH of 7.0 at all temperatures. 

Redox or ORP is expressed in millivolts (mV). A range of -1999 mV to +1999mV is common with ORP instruments.

Redox or ORP measures the total activity of a solution in mV or the total of reducing and oxidizing activities in a solution. Redox or ORP measurement ORP is useful for monitoring and controlling the addition of oxidizing agents such as chlorine, bromine, and ozone or reducing agents including cyanide, sodium bisulfite and metabisulfite.

A Redox electrode does not have to be “calibrated” but it can be tested if required by using a Standard Redox or ORP Test Solution. LTH can offer a suitable Redox test solution. Please contact our sales department with your request.

A Dissolved Oxygen sensor must be at least 15° above horizontal to consistently function properly. The liquid in the sensor contains small air bubbles. If not inclined slightly above horizontal, a bubble can adhere to the cathode where it will affect the sensor’s performance.

The Galvanic cell consists of two electrodes and an electrolyte. A galvanic electrode produces its own current. A silver or gold cathode and a lead anode are immersed in an Alkali electrolyte with a gas permeable membrane separating the sensor from a test solution.

Polargraphic electrodes have a silver anode and a Platinum or gold cathode. A voltage is applied to the electrode to bring about a polargraphic reduction of the diffused Oxygen. A “Polarizing” voltage is provided by the Dissolved Oxygen instrument.

The membrane permeability is temperature dependent, so to obtain accurate measurements of oxygen solubility temperature compensation is applied by the instrument. The effect is large, in the order of 6-7% per °C, so considerations must be made to allow stabilisation of the sensor when calibrating or taking measurements if temperature changes are taking place.

Oxygen saturation of water is different at different pressures. Correction charts are provided in most instruction manuals. Many instruments automatically compensate for barometric pressure. The barometric pressure is either measured by the instrument or manually entered by the user.

Zero calibrate the probe by immersing it in a saturated solution of sodium sulphite. For full-scale calibration the sensor can be calibrated in free air.

POINT LEVEL: Product level distance measured from the tank or vessel’s bottom.
HIGH LEVEL: Maximum level at which “vessel full” indication is required.
LOW LEVEL: Minimum level at which “vessel empty” indication is required.
HIGH HIGH LEVEL: Above maximum expected level, can be an additional high alarm set point to initiate emptying of a tank.
LOW LOW LEVEL: Below minimum expected level, can be an additional low alarm set point to initiate filling of a tank.
PUMP CONTROL LOGIC: When applied to overhead tank level control, the pump is STOPPED if the level is equal to or greater than the maximum desired level and does not RESTART until the level is equal to or less than the minimum desired level. Thus the level is maintained between the minimum and maximum point levels.

If applied to sump level control, the pump is STOPPED when the level is equal to or less than the minimum desired level and RESTARTED when it is equal to or greater than the maximum desired level. Thus the level is maintained between the minimum and maximum desired levels.

Yes, Ultrasonic level transmitters can also be used for Open channel flow measurement.

Ultrasonic measurement provides a non-contacting technology for distance measurement which can be configured to provide accurate continuous measurement of product depth / height. Ultrasonic measurement provides maintenance free height or depth measurement of solids, chemicals and water, from food ingredients to corrosive chemicals, waste water and sewage. As this technique makes no contact with the material, there is no on-going cleaning, wear or maintenance schedule.

The application to avoid with ultrasonic level are extreme foam, vapour or turbulence. Foam, vapour and turbulence can absorb and /or deflect away a substantial portion of the return signal.

Radar operates without influence on the signal by either vapour, temperature or pressure. There is also no effect on the measurement by material changes such as density, dielectric properties, and viscosity. Radar level transmitters are non-contacting, reducing maintenance and service to a minimum. Radar is one of the most widely effective level measurement techniques available.

The working of these meters is based on Faraday’s Second Law of Electromagnetic Induction. It states that, a conductor moving in a magnetic field with the direction of its motion perpendicular to the magnetic field generates an EMF across it and the direction of the EMF is perpendicular to both, the magnetic field and the direction of motion. The generated EMF is proportional to the magnetic flux density, B, the velocity of conductor v and the length of the conductor l. In the flow meter the magnetic field is generated by exciting the coils and the conductor is the liquid itself, under measurement with the length equal to the diameter of pipe.

The electrical conductivity of the liquid to be measured should have a minimum conductivity of 5 µS cm (microsiemens/cm)

The pipe not completely full during operation
Entrained air in the liquid
Pulsating flows
Grounding issues which can include:
PVC or internally lined pipe requires grounding rings
Faulty ground connection

Grounding rings are stainless steel rings with an internal diameter matching the magflow meter ID. If required a pair of grounding rings are required, one on the inlet side and one on the outlet side of the meter body between the flange mountings. Gaskets are required on both sides of each grounding ring.

Grounding rings are required when the piping material is not electrically conductive, such as PVC or cement lined ductile iron pipes. A wire connection must be made to both grounding rings and to the meter body flanges.

Yes, it is always recommended to use gaskets to ensure a good seal to the flange connections. If grounding rings are used then gaskets are a must.

Yes, it is possible to use the Smag flowmeter which has a Stainless Steel 304 body and either a DIN or clamp process connection.

The SGM-100 utilizes two transducers which work as ultrasonic transmitters and receivers. They are clamped on the outside of a closed pipe at a specific distance from each other. They can be mounted in a V position (the sound crosses the pipe twice), in a W position (the sound crosses the pipe 4 times) or in a Z position (mounted on opposite sides of the pipe – the sound crosses the pipe once). The selection of the mounting position depends on the pipe and liquid characteristics.

The SGM-100 operates by alternately transmitting and receiving a frequency modulated burst of sound energy between the two transducers and measuring the transit time that takes the sound to travel between them. The difference in measured transit time is directly and exactly related to the velocity of the liquid inside the pipe.

Yes, ultrasonic clamp-on flowmeters can be used to measure the flow of a wide range of electrically conductive and non-conductive liquids.

It is possible to select the pipe material and lining type in the instrument menu.

No, the four beam alternating light sensors self-compensate for component ageing, sensor fouling and daylight interference

We transmit light directly through the polymer sensor housing so there are no lenses to allow liquids to leak in.

Yes we have 3A certified sensors. Our range of sensors covers both immersion and sanitary applications.

Yes, the sensors have been designed to withstand the rapid temperature cycling which occurs during CIP cleaning cycles.

Yes, the installation and positioning of the sensor is important; for best results refer to the Suspended solids sensor installation guide.

To best control or monitor your application it is best to set up and calibrate against samples of the measured product.

This makes the products rugged, durable and easy to clean as well as suitable for use in the food, beverage and pharma industries.

No – they have active temperature compensation.

We have more than 50 type of process connection available; please contact our sales department with your request.

Gauge pressure

Strong and small diaphragm, Laser welded, Standard polished, minimum oil filling between sensor and diaphragm by using the Flush Diaphragm Technology. Wave structure (back-up) behind diaphragm, Equal to diaphragm structure.Good protection against overpressure with Perfect long term stability. The Pressure sensor is very close to the process

There is minimum oil filling between the sensor and diaphragm by using the Flush Diaphragm Technology. This reduces sensitivity from temperature fluctuations. Produces a reduction in spares / accessory costs by using less oil. Uses a Smaller diaphragm which is less sensitive for damaging.

Ceramic diaphragms are not polished and have a raw / rough finish,
The ceramic diaphragms can be attacked by Nitric Acid
With ceramic diaphragms there is no protection against pressure spikes

The O-ring’s have the following problems:
The O-ring grows old & must be periodically replaced on Ceramic Diaphragms
The O Rings are not gas tight and cannot withstand all media