A few years ago, we were developing a clamp photometer, a handheld device that clips the presence, direction of propagation, and combination of low frequency test tone modulation on a communication fiber. With the clamp photometer, we can correctly identify the special fiber in the manhole or pole tent before fiber cutting and splicing, so as to avoid accidental disconnection of the real-time communication fiber due to identification errors.
The fiber is clamped to a V-shaped block with a small spring pressure at the bend. The bend is designed such that a small amount of internal signal can escape through the more transparent protective layer material, and a pair of photodiodes disposed at both ends of the bend detect the released light. The direction of light propagation is determined by the photodiode that receives the strongest signal. For the most sensitive low-level signal detection, the amplifier needs to operate in the microvolt region, making the chopper-stabilized op amp an essential element for the lowest input offset voltage.
This might seem like a simple method—applying a photodiode signal to a chopper-stabilized analog comparator to determine direction. However, there is a small problem: if there are bidirectional signals in the fiber, such as bidirectional signals for coarse wavelength division multiplexing (1310nm and 1550nm in the opposite direction), we would want the LEDs in both directions to be bright. stand up. Of course, a comparator that chooses only one state cannot achieve this goal.
The circuit in the figure solves this problem by: when there is a big difference between the two signal levels or when one of the signals does not exist, only the LED indicator in the appropriate direction is illuminated; when the signal level of the LED is very When approaching, the LEDs in both directions are illuminated, and the required threshold depends on the mechanical design of the fiber holder beyond the DI range. If no signal appears in either direction, both LEDs are off, indicating a dark fiber.
In this example, the ICL7650S Chopper-stabilized operational amplifier is used in accordance with the hardware configuration of the original manufacturing country; in actual production (the necessary external voltage-stabilizing capacitor is omitted in the figure for clarity), other types of Operational Amplifier. A bias voltage of about 1 V is set in the diode D1 connected in series as a zero signal reference voltage. In the absence of an input signal, R15 maintains the voltages of comparators U3 and U4 at a low level, approximately +2 mV from the reference voltage.
The circuit is easy to operate. Each photodiode operating in photovoltaic mode causes the respective transimpedance amplifiers U1 and U2 to output a voltage that depends on the intensity of the detected light. The voltages of each level are applied to comparators U3 and U4. By comparing the output voltage of the transimpedance amplifier of buffer U5 with the larger overall gain, the comparison voltage level can be derived. Therefore, the level value is the maximum photodiode level divided by R5 and R1 2 divided by the minimum photodiode level to accommodate large variations in signal levels within the fiber. As the value of the resistor appears, as long as the difference between the lower photodiode current value and the higher photodiode current value is not less than 0.22x, the LED indicating the two signals will be bright; if the difference between the current values Below 0.22x, only the LED indicating the strongest signal is on.
Heater means for heating equipment. The heater can be divided into several types due to the different of heating principle, heating channels, thermal conductivity media and scope. Our factory produce and sale Gas Heater, electric heater, Kerosene Heater. The heater is easy to remove and heating, are widely used in homes and public places. Our gas heater use imported heat-resistant fire net, net life more than 10years; The heater use pure copper valve core, pure copper gas tube, pure copper spay nozzle, durable and no leakage; Our heater have dual heating function with flame control lever, heater and cooker 2 in 1; The heater use steel body, all steel thickness more than 0.6mm, sturdy and durable; The heater`s piezoelectric ignition switch, life can be over 30000 times.
1. imported heat-resistant fire net, net life more than 10years.
2. pure copper valve core, pure copper gas tube,pure copper spay nozzle, durable and no leakage, longer life more than 10 years.
3. dual heating function with flame control lever, heater and cooker 2 in 1, whole unit life more than 10 years.
4. moderately dry your room, purifying the environment, effectively inhibit the growth of bacteria.
5. steel body, all steel thickness more than 0.6mm, sturdy and durable.
6. exquisite outline, easy handhold design, portable anywhere at your disposal.
7. steel surface treatment by ECO electroplating technique to avoid steel rust.
8. piezoelectric ignition switch, life can be over 30000 times.
9. fire or gas can be turned up and down freely.
10. unbreakable, shock-resistant, sturdy, durable package to ensure product transit safety.
Gas heater is divided into: umbrella-shaped gas heater and cabinet-type mobile gas heater. These two gas heaters are classified into liquefied gas and natural gas according to applicable fuels. Umbrella gas heater which is also known as outdoor heating, outdoor gas heater, umbrella heater, gas heating stove, lamp heater, umbrella heater, umbrella heating furnace.
Gas Heater
Portable Gas Heater, Gas Room Heaters, Gas Heaters For Home, Indoor Gas Heaters, Small Gas Heater
Ningbo APG Machine(appliance)Co.,Ltd , http://www.apgelectrical.com