Dear Rocío Esquembre

The count rate represents the average scattering intensity during the measurement with a particular sample under a specific optical settings of the experiment. Then you can judge the concentration of your sample and maybe dilute it.

Kind Regards

Qamar Ul Islam

Hello Rocío Esquembre , the attenuator should find a position such that the count rate is somewhere between 100-500 kcps.

When you insert a sample in a DTS0012 cuvette of just very clean water - what count rate do you get? What count rate do you get when there is nothing in the sample holder and you make a measurement?

You could also take a measurement of your sample with fixed attenuator at attenuator 1. This should give a very low count rate. If it is still more than 10000 kcps then this may mean that either your attenuator is not moving or the detector is broken.

Can you take a data file with attenuator position 1 and just 3 correlation functions,

Measurement - Manual 3 runs of 5 seconds, put a checkmark next to Partial Results "allow results to be saved containing correlation data only"

Advanced - automatic attenuation No - Attenuator 1

and share the dts record data file?

I would recommend to check the equipment using the latex standard sample. Then, try the suggested steps above.

Best wishes

Hi Rocio. Agree with Ricardo, you need to check with the latex standard as well. My Zetasizer got the same problem (count rate too low) but with all samples. The engineer came and found that it was due to the APD Module and DSP Board problem. They have changed it and now it is fine (the cost is quite expensive though). The engineer also suggest me to use UPS if there might have voltage spike or sustained overvoltage to the equipment in the future.

Thanks for all the answers. We have checked that the count rate is always higher than 10000 kcps, even in sample absence.Attenuator seems to move (sample count rate changes by using different attenuators). We have performed the indicated measurement (manual with attenuator 1...) and we share the file. We hope it won´t be an APD module problem. We use a surge limiter but it isn´t an UPS

Hello Rocio, thanks for the measurement. This does - unfortunately - look like either a malfunctioning signal processing/correlator inside the system or the APD or both. I hope your local Malvern Panalytical service/support team can resolve the issue for you.

Thanks again. We've already contacted our service support team. Let's keep our fingers crossed and hope for the best!.

Thanks to all again . One last question Norhayati Mohamed Noor , How old was your DLS instrument? Ours it's just two and a half years old and we are surprised that it can be such a significant damage.