PME type photoelectric automatic particle counterDetailed product description：

The PME type grain counter can automatically count the grains of various major grain crops, such as rice, wheat, sorghum, corn, etc. It is widely used in agricultural colleges, seed systems, grain departments, to investigate seed indicators and measure thousand grain weight.
Main technical performance
1. Counting varieties:
PME type:
(1) The dimensions are less than 12 x 4 millimeters in length and width (for small particles);
(2) Size: length x width less than 12 x 10 millimeters (for large particles)
PME-1 type
Size: length x width less than 12 x 4 millimeters (small particles)

2. Counting accuracy: ± 4/1000 depending on speed. (Standard deviation)
3. Counting speed: Small particles larger than 1000 particles per 3 minutes; 500 large particles/3 minutes
4. Counting capacity: 1~9999 is directly read by a four digit LED digital tube.
5. Self calibration frequency: f=1~2HZ, f=10~20HZ
6. Pre set self stop: any value between 1 and 9999, set to 0000 without counting.
7. External power supply 220~± 20V~50HZ, power less than 20 watts, well grounded.
8. Instrument size: 304 × 234 × 180 millimeters.
9. Working environment: Atmospheric pressure: 750 ± 30 mmHg.
Environmental temperature: 0 ℃~40 ℃
Relative humidity: less than 80% at 20 ℃
Continuous use time: greater than four hours.
10. Instrument functions: Circuit self calibration, arbitrary counting, preset self stop, automatic door extraction and feeding self-locking.  

Instrument working principle
The electromagnetic vibration box causes seeds to be queued and fed one by one, forming photoelectric pulses after falling into the photoelectric conversion tank. After amplification, shaping, and inversion, they are sent to the counting circuit and displayed on an LED digital tube for reading. The preset dial switch stops feeding and counting when the preset number is reached. The instrument is equipped with a self calibration frequency for checking the correctness of the counting circuit and preset settings. The box is shown in Figure 2:
Figure (2) Block diagram of PME particle counter
(1) Electromagnetic vibration feeding device: The seeds are placed on the tray, and the chute is spiral shaped.
(2) The seeds rising in the spiral groove reach the feeding port and fall down. They are projected onto the silicon photovoltaic cell through the photoelectric conversion area to generate current changes. After pulse amplification and shaping, the photoelectric counting pulsation is obtained and sent to the counting circuit for counting display.
(3) The counting display circuit adopts CC4518 (HEF4518 from Philips) dual BCD counter, and uses CC4511 ("HEF4511") BCD-7 segment latch/decode/driver to decode and drive the common negative LED display. The four digit LED input terminal is connected in series with a current limiting resistor to ensure uniform stroke brightness. The CC4518 counting input terminal has a clock terminal (CL), a clock enable terminal (EN), and a reset terminal (R). When the single digit number is EN="1" (high voltage level), the counting pulse is input by "CL" and triggered by a positive jump. The last three bits are all CL="0" (low level), input by EN and triggered by a negative jump.
(4) The control signal of the preset self stop circuit is connected to the NAND gate at the four input terminals through a switch diode, a dial switch, and a finger wheel. When the preset number of the dial matches the counting number, the relay is activated to cut off the counting input, ground the counting input terminal, stop feeding, and the LED displays the preset number.