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The distinction and characterization of noise have been carried out in the current mirror (CM) circuit as a part of a biosensor system with some main components of MOSFET type BS250 and two resistors at the input (Rref) and output (RL) of the circuit. This evaluation is important since the biosensor module has very high impedance due to the low conductivity sample measured and the high loading resistance for current to voltage conversion. This high impedance leads to the rise of high noise due to thermal noise which is proportional to the resistance, in addition, the type and the specifications of the MOSFET determine the noise due to semiconductor properties. Therefore, this evaluation can be used to reduce the resulted noise to obtain high Signal to Noise Ratio (SNR). The experiment was performed by applying Rref and RL with some values of 1 kν, 100 kν and 1 Mν while maintaining the voltage source at 1 V, which causes the input current to vary accordingly. This experiment was adjusted to meet the range of current in the biosensor application, which is relatively very small. The measurement is acquired by a DAQ card PCI-6221 that has been integrated with a LabVIEW program based on Fast Fourier Transform (FFT). The noise response analysis is performed within a bandwidth of 0.1 Hz to 100 kHz and a frequency resolution of 0.1 Hz. This bandwidth is sufficient to describe the noise in the CM circuit applied to the biosensor device. The results show that the noise characteristics vary with the applied resistance. Thus, it can be considered to determine an appropriate loading resistance, which could be used to build a high SNR current mirror circuit for the biosensor system. [ABSTRACT FROM AUTHOR]

An algae-based biosensor is investigated using dissolved oxygen levels producing from photosynthesis mechanism and from photoperiodism response time which describes the plant's reaction to light. This paper presents the sensitivity factor in the form of dissolved oxygen rate production level and response time of green algae-based biosensor, which is stimulated using artificial light of LEDs blue (480 nm) and red (650 nm). An amperometric electrode with two green algae as bioreceptors Chlorella kessleri and Chlorella sp. were tested in the biochip C chamber. A sample of 150µL algae with a density of 5−105 cells/ml was illuminated by the artificial light of blue and red spectrum altered for 1000 seconds of the dark-light cycle. The results showed a significant difference in the sensitivity of the algae chlorella sp. in producing dissolved oxygen which is 6.3 and 12.9 times higher than the chlorella kessleri for the blue and red light. While the photoperiodism response of Chlorella sp. has a time constant of 49.8 % for red and 37.5 % for blue smaller than Chlorella kessleri respectively. This result shows the algae chlorella sp. possesses good response characteristics to the red light, but less for photoperiodism response. [ABSTRACT FROM AUTHOR]

This paper reports optimization of an LVDT output signal using phase synchronization adjustment. The output signal of an LVDT that incorporates its sign or displacement direction are usually obtained by using a synchronization between the excitation and secondary output signal using a phase-sensitive rectifier. However, the phase of the excitation signal might not be perfectly matched with the phase of the second output signal of LVDT. This causes the rectifier to pass a small portion of the opposite polarity signal beyond the zero lines. Consequently, the total output signal after integration to a dc signal could be reduced, which yields a reduced sensitivity. The implementations of the phase synchronization adjustment methods could improve the performance of the output of the LVDT. The adjustment removes the signal beyond the zero line; thus, the dominant signal is not subtracted due to the leaked opposite sign signal. The adjustment of the phase synchronization to a certain phase angle provide the optimum sensitivity of the output of the LVDT and increase the sensitivity to 15% higher than the sensitivity without adjustment or zero phase shift. [ABSTRACT FROM AUTHOR]

Algae are very important to the life of human as a bio-indicator of water pollution. The observation of algae vitality can give information of the environment changes of the algae, which are shown by the changes of parameter in its environment. This study is aimed to observe the influence of toxicity of herbicide 2,4-D dimethylamine 865 SL on the vitality of algae species Chlorella Kessleri in producing dissolved oxygen as a result of photosynthetic mechanism. A 50μL herbicide 2,4-D dimethylamine 865 SL with a concentration of 10 % was added into immobilized algae in the Biochip-C from cellasys GmbH and stimulated with artificial light of 400-700 nm for photosynthetic process. The effect of herbicide 2,4-D dimethylamine 865 SL was observed and shows the increase of the basal potential after 1500 s, which indicates the dissolved oxygen reduction in the environment of the algae. This effect is reversible and a restoration of the photosynthetic activity take place after the substance removal. The use of this toxin is systemic, which slowly kill the living cells. [ABSTRACT FROM AUTHOR]