Frequently Asked Questions
Commercial QuestionsHow do I open an account with DD Scientific ?
If you wish to open an account with DD Scientific, please send a title purchase order to admin@ddscientific and we will be pleased to create a pro-forma (pay in advance) account. Credit terms are typically only available to customers who have placed and paid for 3 purchase orders previously.
What are your hours of business ?
Our facility in the UK is open 8.30am until 5.00pm Monday to Friday.
What are your credit terms ?
Our credit terms are typically 30 days from date of invoice. Credit accounts are typically provided to customers who have already placed orders and paid on a pro-forma basis at least three times. At that point, a credit account may be requested and will be provided at our discretion and subject to satisfactory trade references.
Can you provide customer specific products ?
Of course. One of DD Scientific’s key differentiators is our willingness and ability to provide customisation to customers. Whether this is a simple requirement such as a bespoke label or more involved such as custom outputs, performance characteristics or different colour mouldings we are always very happy to discuss. We do however assess all customisation on the basis of potential and realistic volume requirements - if we are unlikely to recoup any development costs through normal use of the product, we may choose to ask for a non-recurring expenditure (NRE) contribution up-front or we may decide to refuse.
I have an instrument which is using one of your sensors - can I buy a replacement so as to be able to replace it ?
For many reasons, we prefer to deal only with OEM manufacturers of detectors and instruments. There is a risk of the certification of your instrument being compromised if you do not use replacement sensors sourced from the instrument manufacturer (even if they are DD Scientific sensors).
What are the lead times for delivery of sensors ?
Lead times vary between product types and order quantities. Our typical lead times for high running products such as oxygen, carbon monoxide and hydrogen sulphide sensors are rarely longer than 2 weeks from receipt of order. Lower volume or more exotic gas sensors may take longer but the maximum lead-time for any sensor should not exceed 4 weeks unless we are seeing particularly high demand for that product.
What is your warranty returns procedure ?
Our process is straightforward - if you have product which you believe is faulty, then please email testing@ddscientific.com stating which sensor types and what the reported fault is. You will then be issued an RMA number - please return the products at your cost to DD Scientific and we will complete a thorough examination. If the sensors are found to be faulty, then we will refund the freight costs as well as provide you either with replacement product or a credit to your account, whichever you prefer.
How can I tell how old a sensor is ?
Date codes are provided on all DD Scientific sensors upon the label. This date details when the sensor was manufactured and may not necessarily link to the date of shipment.
Do you store your end of line test data and is it available to customers ?
The test data for every single sensor produced at DD Scientific is uploaded to our central database. Given a serial number, we can provide the test data for any sensor. Contact sales@ddscientific.com for more information.
How many people work at DD Scientific ?
In total, our workforce is just under 100 people. Within our engineering and management team, we have more than 250 years experience of the development, manufacture and sale of gas sensors.
How long has DD Scientific been in operation ?
DD Scientific was founded by Daniel Davies, an expert in sensor electrode fabrication, in 2011 in response to unmet OEM needs for high performance electrochemical gas sensors at a realistic price. Since 2011, DD Scientific has been growing strongly in the industrial safety, residential safety and medical fields and our products are becoming more and more the de facto choice for instrument manufacturers worldwide.
Do you use distributors in other countries ?
We have a range of distributors in a number of territories - these distributors have been carefully selected and in many cases, trained on-site at DD Scientific so as to be able to provide world class technical and commercial support, as they would receive if DD Scientific dealt with them directly.
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Technical QuestionsHow often should a sensor be calibrated ?
The calibration period for a sensor will depend on a number of factors such as the environment in which it is used, operating temperature, humidity, atmospheric pressure and environmental pollutants. In all cases we recommend sensors are calibrated in line with target market legislation. Typical calibration intervals are 3 months or 6 months. Some of our sensors such as the S+2ECO are designed to be installed for very long periods without calibration - in these cases the drift characteristics of the sensors are very well known and can be relatively easily compensated for.
What does cross sensitivity mean ?
The catalysts used in any electrochemical sensor have the potential to catalyse the oxidation or reduction of gases other than the target gas. For example, most carbon monoxide sensors will show sensitivity to hydrogen. Where possible DD Scientific attempt to develop gas sensors with as low as possible cross sensitivity to other gases at the chemistry level, and where it is not possible we provide filters inside the sensors to remove interferences. For every sensor that DD Scientific produce, we provide a list of the known cross interferences so that users can review and plan around them.
Can I put a membrane or dust cover in front of a DD Scientific sensor ?
The majority of DD Scientific sensors are provided with a PTFE cover on the front to prevent dirt and water entering. The addition of further dust covers and/or membranes will have an impact on how fast the sensor can respond to changes in gas concentration.
Does temperature affect DD Scientific sensors ?
The chemical reactions which take place inside an electrochemical sensor are affected by the ambient temperature. As a result, both sensor baselines and sensitivities can change with changes in temperature - and in some cases can be quite significant. However with adequate compensation within an instrument, the errors resulting from these changes can be minimised to low levels. DD Scientific is able to provide detailed temperature data for any of our sensors - please do not hesitate to contact us for this information.
At what atmospheric pressure can I use DD Scientific sensors ?
All of our sensors are specified to 1000mbar +/- 100 mbar which will allow the sensors to be used in most applications. The output of our electrochemical sensors is independent of the atmospheric pressure, but rapid pressure changes can cause small spikes in output which soon recover. If you wish to use DD Scientific sensors outside of their pressure specification, please ensure that pressure (or vacuum) is not applied only to the front of the sensor as this can result in possible ruptures of internal sealing mechanisms and electrolyte leakage.
How should I store DD Scientific sensors ?
We recommend that our gas sensors are stored in a clean, relatively dry environment free from atmospheric poisons such as silicone or solvent vapours. Many of our customers store sensors in refrigerators - this is perfectly fine although not necessary.
What happens if I expose a sensor to high levels of target gas ?
When a sensor sees a high gas concentration, namely that beyond its specified maximum overload value, it is possible that it will not be able to oxidise or reduce all of the target gas. In this case, the sensor’s internal reference electrode may become affected and the signal may collapse. In this case, the sensor should be allowed to re-settle in clean air or zero gas - this process can take a few minutes to occur.
DD Scientific sensors will not be damaged by exposure to high levels of target gas. Why does your recommended circuit for toxic sensors include a JFET?
The JFET is present to ensure that the potentials of the sensing and reference electrodes remain at the same potential during instrument storage and transit. This minimises the settling time of the sensor when power is applied to the drive circuitry and means that the sensor will be ready to measure gas within a few minutes or less. For suggested JFETs, please visit InterFET.
Note that it is not recommended to add a JFET to biased sensors (such as NO or lead free O2 sensors). |