Answer
Jan 22, 2024 - 12:09 PM
There there separate questions which I will answer individually.
1) What is the frequency for the output signal? - The limitation on how fast the output will update is the response time of the sensor. The sensor is a capacitance type sensor which changes capacitance as it absorbs moisture. The rate at which the sensor absorbs moisture depends on the environment. If you are measuring the humidity or dew point temperature of still air, the sensor will respond more slowly than fast moving air. Normally we see response times of 10- to 30sec for a 63% step change.
2) Is the cable just normal copper twisted pair cable? - The output cable is not twisted pair. You normally use a twisted pair cable to minimize the affect of electrical noise in the environment. That is important for signal cable carrying low level voltages. The output of the HDR200 is a 4-20mA signal which is resistant to electrically noisy environments so twisted cable is not required.
3) May I know the impedance or any spec of the cable that the sensor uses? - The HDR200 output cable is one foot of 24 AWG copper cable, but I think the question really is about the impedance the HDR200 output can drive into. The HDR200 is a two wire loop powered device with a 4-20mA output. This means the signal and power travel along the same pair of wires. The HDR200 requires 12-28Vdc to operate. Since the power supply and reading device are connected in series on the same pair of wires, you would need to use a power supply that has a voltage so that the HDR200 will still receive it operating power after the voltage drop caused by the wire and reading device. Here is an example:
Assume you are using a 24Vdc power supply and 100' of 24awg cable attached to the output of the HDR200. The cable resistance will be about 6 ohms. Since the maximum current output of the HDR200 is 20mA, the voltage drop over the 100 ft of output cable according to ohms law(V=IR) will be ~ 100*20/1000 or 2 volts. Since you are using a 24V power supply and the HDR200 needs at least 12 volts to operate you can afford a maximum voltage drop of 10 volts (24V-12V-2V) across your reading device. Since the maximum current is 20mA that means the maximum voltage impedance of your reading device by ohms law is 10/20*1000(R=V/i) = 500ohms.
1) What is the frequency for the output signal? - The limitation on how fast the output will update is the response time of the sensor. The sensor is a capacitance type sensor which changes capacitance as it absorbs moisture. The rate at which the sensor absorbs moisture depends on the environment. If you are measuring the humidity or dew point temperature of still air, the sensor will respond more slowly than fast moving air. Normally we see response times of 10- to 30sec for a 63% step change.
2) Is the cable just normal copper twisted pair cable? - The output cable is not twisted pair. You normally use a twisted pair cable to minimize the affect of electrical noise in the environment. That is important for signal cable carrying low level voltages. The output of the HDR200 is a 4-20mA signal which is resistant to electrically noisy environments so twisted cable is not required.
3) May I know the impedance or any spec of the cable that the sensor uses? - The HDR200 output cable is one foot of 24 AWG copper cable, but I think the question really is about the impedance the HDR200 output can drive into. The HDR200 is a two wire loop powered device with a 4-20mA output. This means the signal and power travel along the same pair of wires. The HDR200 requires 12-28Vdc to operate. Since the power supply and reading device are connected in series on the same pair of wires, you would need to use a power supply that has a voltage so that the HDR200 will still receive it operating power after the voltage drop caused by the wire and reading device. Here is an example:
Assume you are using a 24Vdc power supply and 100' of 24awg cable attached to the output of the HDR200. The cable resistance will be about 6 ohms. Since the maximum current output of the HDR200 is 20mA, the voltage drop over the 100 ft of output cable according to ohms law(V=IR) will be ~ 100*20/1000 or 2 volts. Since you are using a 24V power supply and the HDR200 needs at least 12 volts to operate you can afford a maximum voltage drop of 10 volts (24V-12V-2V) across your reading device. Since the maximum current is 20mA that means the maximum voltage impedance of your reading device by ohms law is 10/20*1000(R=V/i) = 500ohms.
