| 摘要 |
PURPOSE:To obtain a highly practical apparatus for determining pH, of a light transmission system barely affected by induced noizes, by using a liquid crystal as a photomodulating element, and subjecting pH-detecting signals to the light transmission/interruption control or absorption/reflection control with pulse width modulated signals. CONSTITUTION:In an oscillating section 2, pH electrodes 6-6, a pulse width modulater 7 for pulse width modulation of detecting signals from the pH electrodes 6-6, and a liquid crystal 8 as a photomodulating element are arranged. Optical reference signals from a light source 3 in a receiving section 1 are transmitted through an optical fiber 9 to the liquid crystal 8. The light passing through the liquid crystal 8 is transmitted through an optical fiber 10 to a demodulator 4. Since, according to such constitution as above, the liquid crystal 8 photomodulates the pH detecting signals with the pulse width modulated signals, the optical reference signals transmitted from the light source 3 through the optical fiber 9 is transmission tion/interruption controlled by the liquid crystal 8. The intermittent light passing through the liquid crystal 8 is made incident to the demodulator 4 through the optical fiber 10, and the incident light is demodulated with the demodulator 4 to analogue signals, to deflect an indicating meter 5. The demodulator 4 is provided with a circuit which converts the pulse width into an analogue amount, and indicates the pH value detected by the indicating meter 5. |
