Photocells, photodiodes, and spectroscopy applications — from bench experiments to plasma-discharge characterization.
Photocell detecting light from plasma processing chamber.
A photocell is a sensor that can measure the intensity of light. Other light sensors are capable of measuring color (spectrum), or detecting modulated sources.
Processing plasma discharge producing detectable light signature.1
Plasma processing is a key technology used in many industries for coating materials from sunglasses, to LCD screens and solar panels. One novel application of light detection is employed to measure the temperature of a processing plasma discharge. Directly measuring a plasma discharge electrically perturbs the discharge itself, so using optical detection method is prefered when permissible. To do so, a DAQ system could be used to collect light intensity at certain wavelengths to determine the excitation signatures of specific noble gasses in the discharge. A Nyquist DAQ device and a few photo sensors (with bandpass coating) could serve this purpose with little physical setup. This could replace thousands of dollars worth of spectroscopy equipment.
1M. V. Malyshev and V. M. Donnelly, “Determination of electron temperatures in plasmas by multiple rare gas optical emission, and implications for advanced actinometry,” Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, vol. 15, no. 3, pp. 550-558, 1997.
Recommended DAQ
Recommended DAQ: Nyquist 2
Optical detection often needs higher resolution than 12-bit to distinguish noise from signal in low-intensity environments. NQ2’s 24-bit ADC gives you the dynamic range; NQ1 works for high-contrast applications.
Code example
The DAQiFi Python SDK exposes a property-based API. Below is a minimal stream — discover the device, enable an analog-input channel, and print samples at 1 kS/s.
from daqifi import DAQiFiDevice
with DAQiFiDevice.discover_first() as dev:
dev.channels.ai0.enable()
for sample in dev.stream(rate_hz=1000):
print(sample)
For C#, Java, LabVIEW, or Node.js examples, see the open-source stack page or jump straight into the reference example app on GitHub.
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