Photomicrosensor Basics: Terminology
The characteristics included within the Photomicrosensor (photointerrupter) datasheets are explained below. The terms are separated by type of output; Phototransistor output or Photo IC output.
Phototransistor Output
| Symbol | Item | Definition |
|---|---|---|
| IFP | Pulse forward current | The maximum pulse current that is allowed to flow continuously from the anode to cathode of an LED under a specified temperature, a repetition period, and a pulse width condition. |
| IC | Collector current | The current that flows to the collector junction of a phototransistor. |
| PC | Collector dissipation | The maximum power that is consumed by the collector junction of a phototransistor. |
| ID | Dark current | The current leakage of the phototransistor when a specified bias voltage is imposed on the phototransistor so that the polarity of the collector is positive and that of the emitter is negative on condition that the illumination of the Photomicrosensor is 0 ℓx. |
| IL | Light current | The collector current of a phototransistor under a specified input current condition and at a specified bias voltage. |
| VCE(sat) | Collector-emitter saturated voltage | The ON-state voltage between the collector and emitter of a phototransistor under a specified bias current condition. |
| ILEAK | Leakage current | The collector current of a phototransistor under a specified input current condition and at a specified bias voltage when the phototransistor is not exposed to light. |
| tr | Rising time | The time required for the leading edge of an output waveform of a phototransistor to rise from 10% to 90% of its final value when a specified input current and bias condition is given to the phototransistor. |
| tf | Falling time | The time required for the trailing edge of an output waveform of a phototransistor to decrease from 90% to 10% of its final value when a specified input current and bias condition is given to the phototransistor. |
| VCEO | Collector-emitter voltage | The maximum positive voltage that can be applied to the collector of a phototransistor with the emitter at reference potential. |
| VECO | Emitter-collector voltage | The maximum positive voltage that can be applied to the emitter of a phototransistor with the collector at reference potential. |
Photo IC Output
| Symbol | Item | Definition |
|---|---|---|
| IF | Forward current | The maximum DC voltage that is allowed to flow continuously from the anode of the LED to the cathode of the LED under a specified temperature condition. |
| VR | Reverse voltage | The maximum negative voltage that can be applied to the anode of the LED with the cathode at reference potential. |
| VCC | Supply voltage | The maximum positive voltage that can be applied to the voltage terminals of the photo IC with the ground terminal at reference potential. |
| VOUT | Output voltage | The maximum positive voltage that can be applied to the output terminal with the ground terminal of the photo IC at reference potential. |
| IOUT | Output current | The maximum current that is allowed to flow in the collector junction of the output transistor of the photo IC. |
| POUT | Output permissible dissipation | The maximum power that is consumed by the collector junction of the output transistor of the photo IC. |
| VF | Forward voltage | The voltage drop across the LED in the forward direction when a specified bias current is applied to the photo IC. |
| IR | Reverse current | The reverse leakage current across the LED when a specified negative bias is applied to the anode with the cathode at reference potential. |
| VOL | Output low voltage | The voltage drop in the output of the photo IC when the IC output is turned ON under a specified voltage and output current applied to the photo IC. |
| VOH | Output high voltage | The voltage output by the photo IC when the IC output is turned OFF under a specified supply voltage and bias condition given to the photo IC. |
| ICC | Current consumption | The current that will flow into the sensor when a specified positive bias voltage is applied from the power source with the ground of the photo IC at reference potential. |
| IFT (IFT OFF) | LED current when output is turned OFF | The forward LED current value that turns OFF the output of the photo IC when the forward current to the LED is increased under a specified voltage applied to the photo IC. |
| IFT (IFT ON) | LED current when output is turned ON | The forward LED current value that turns ON the output of the photo IC when the forward current to the LED is increased under a specified voltage applied to the photo IC. |
| ΔH | Hysteresis | The difference in forward LED current value, expressed in percentage, calculated from the respective forward LED currents when the photo IC is turned ON and when the photo IC is turned OFF. |
| f | Response frequency | The number of revolutions of a disk with a specified shape rotating in the light path, expressed by the number of pulse strings during which the output logic of the photo IC can be obtained under a specified bias condition given to the LED and photo IC (the number of pulse strings to which the photo IC can respond in a second). |
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