I am working working with Agilent Handheld FTIR 4300 and is experiencing some issues with the external and diffusive reflectance modes. I find it really hard to obtain a spectrum of good quality. Before measuring the sample, I collect a background using the suitable cap depending on the surface of the sample. This part is no problem, but when I measure the sample, the energy drops significantly and the spectrum gets very noisy. Further, it seems not possible to adjust the gain, and to even get a spectrum, it is necessary to press hard on the sample.
What can I do to collect a spectrum of good quality?