Tank resonance locator

[Tony Stewart]

Use an LM35

 

[Vijit Dubey]

Use an LM35

reading the datasheet. Give me some time.

 

[Vijit Dubey]

Use an LM35

Isn't this like a thermometer. I mean it would read the ambient temperature but I want to use the thermistor embedded inside the IGBT. I think LM35 defeats my purpose.

 

[Tony Stewart]

Inside as in a Hybrid array like Mitsubishi's IGBT 1 Gigawatt switches.

Diodes are linear, Thermistors are not unless properly designed in a CC array,

Consider a signal diode then. just like CPU's do.

LM35's are very linear.

 

[Vijit Dubey]

Inside as in a Hybrid array like Mitsubishi's IGBT 1 Gigawatt switches.

Diodes are linear, Thermistors are not unless properly designed in a CC array,

Consider a signal diode then. just like CPU's do.

I know the graph is logarithmic. I just want to monitor if the temperature goes beyond a certain point. So, the moment it goes beyond a certain frequency I need an alarm.

 

[Tony Stewart]

Sorry I lost track of your design for these measurements.

I cant see the scope of the project and why you chose v to f then f to v to detect an alarm condition. Certain EMI issues of ingress must be corrected.

 

[Vijit Dubey]

Sorry I lost track of your design for these measurements.

I cant see the scope of the project and why you chose v to f then f to v to detect an alarm condition. Certain EMI issues of ingress must be corrected.

I didn't follow what you meant by v to f and f to v.
I will be monitoring digital input 1 to know the switching rate and know which IGBT thermistor I am on right now(to know which PLC am I on right now). I'll be using digital input 2 to measure the frequency (as R changes) and measure temperature if it goes beyond a certain limit.

How can I filter the EMI?

 

[Tony Stewart]

I cant see your system design, but low impedance analog might be easier and faster to commutate than a thermistor controlled frequency (V to F or rather R to F)

 

[Vijit Dubey]

I cant see your system design, but low impedance analog might be easier and faster to commutate than a thermistor controlled frequency (V to F or rather R to F)

The concern with analog (voltage) is that if any IGBTs blow. Previously, I was using a voltage bridge. How do I isolate and make sure they don't blow other IGBTs aor PLC.

PS2501-4 will give me isolation upto 5KV rms.

This is the attachement of schematic for board.

 

[Tony Stewart]

I might recommend Mitsubishi J-Series T-PM IGBT, diode integrated on IGBT chip is used to detect chip temperature directly and enable to turn off IGBT safely and fast for over-temperature protection. But I dont know if that meets your requirements.

 

[Tony Stewart]

**broken link removed**