help with the flow sensor FS5

The signal should not change quickly - if it is changing rapidly, then it is most likely noise.

The base of the transistor, which is connected to the output of the op-amp, should be  about .7 volts higher than the transistor emitter, which is connected to the resistor bridge.

It looks like the emitter voltage should vary between about 5 volts and 7.5 volts depending on the flow rate (temperature).

From your description of the voltages, it sounds like the voltage at the + input of the op-amp is too low. check to see that all resistors have the correct values and that the sensor and heater pins have not been reversed.

What are the voltages on the input and output pins of the first op-amp?

Referrng to FS5A flo sensor i have followng queries

1) i fitted fs5A flow sensor in a 12.5mm pipe(inner diameter) 6 feet in length.i opened valve and air flow started flowng through pipe.i read 6 volts at output of cicuit (evaluation board circuit). Now from this 6 volt at at output how can i calculate air velocity at 25 C temperature? Any relation?

2) secndly using king's law what is value of  "k" in that kings law with units

Anyone help me please i will be grateful

Referrng to FS5A flo sensor i have followng queries

1) i fitted fs5A flow sensor in a 12.5mm pipe(inner diameter) 6 feet in length.i opened valve and air flow started flowng through pipe.i read 6 volts at output of cicuit (evaluation board circuit). Now from this 6 volt at at output how can i calculate air velocity at 25 C temperature? Any relation?

2) secndly using king's law what is value of  "k" in that kings law with units

Anyone help me please i will be grateful

Referrng to FS5A flo sensor i have followng queries

1) i fitted fs5A flow sensor in a 12.5mm pipe(inner diameter) 6 feet in length.i opened valve and air flow started flowng through pipe.i read 6 volts at output of cicuit (evaluation board circuit). Now from this 6 volt at at output how can i calculate air velocity at 25 C temperature? Any relation?

2) secndly using king's law what is value of  "k" in that kings law with units

Anyone help me please i will be grateful

Referrng to FS5A flo sensor i have followng queries

1) i fitted fs5A flow sensor in a 12.5mm pipe(inner diameter) 6 feet in length.i opened valve and air flow started flowng through pipe.i read 6 volts at output of cicuit (evaluation board circuit). Now from this 6 volt at at output how can i calculate air velocity at 25 C temperature? Any relation?

2) secndly using king's law what is value of  "k" in that kings law with units

Anyone help me please i will be grateful

Referrng to FS5A flo sensor i have followng queries

1) i fitted fs5A flow sensor in a 12.5mm pipe(inner diameter) 6 feet in length.i opened valve and air flow started flowng through pipe.i read 6 volts at output of cicuit (evaluation board circuit). Now from this 6 volt at at output how can i calculate air velocity at 25 C temperature? Any relation?

2) secndly using king's law what is value of  "k" in that kings law with units

Anyone help me please i will be grateful

Hi,

I have a stupid question. Is the FS5 sensor supposed to be mounted perpendicular to or parallel with the direction of airflow?

Long thin edge facing the flow (perpendicular to the flow vector)  - do not block the flow when mounting.

Dear Douglas,

In 5 pin opamp, what is the part number of it?

Why 2 pins are not connected which is used for operations?

Your early reply highly appreciated

Air velocity is not linearly proportional to output voltage. You would need to calibrate against a known measurement method.

The curve will look something like this one:

http://www.farnell.com/datasheets/484569.pdf?COM=Discussions

I think k is the thermal conductivity of air:

https://www.engineeringtoolbox.com/air-properties-d_156.html