 Mark as New
 Bookmark
 Subscribe
 Mute
 Subscribe to RSS Feed
 Permalink
 Report Inappropriate Content
Hello,
I tried to measure the Temperautre, but the room temperature is shown 85°C instead of 25,20°C . I don't know where the Problem could be.
Best Regards
Tarik
Solved! Go to Solution.
 Labels:

PSoC 5LP
 Mark as New
 Bookmark
 Subscribe
 Mute
 Subscribe to RSS Feed
 Permalink
 Report Inappropriate Content
I did a simple stepbystep test for R_referense = Rx = 100 Ohm:
at line vRef = MeasureRefResVoltage ();
result = 80 mV (LCD_Position (0,0); LCD_PrintU32Number (ADC_DelSig_CountsTo_uVolts (vRef));)
should be 100mV but this is acceptable.
at line rtdRes = GetRTDRes (vRef);
result = 124500 this corresponds to 63.3 degrees and I see it on the display (RTD Temp = 63.30).
There seems to be a problem in the int32 function GetRTDRes (int32 vRef)
possibly function zeroCurrentOffset = GetOffset (); gives the wrong result.
zeroCurrentOffset = 1300 but should be around 13000.
A similar problem was solved in this thread: Calculating RTD sensors
 Mark as New
 Bookmark
 Subscribe
 Mute
 Subscribe to RSS Feed
 Permalink
 Report Inappropriate Content
Tarik,
I've downloaded your project. It's mostly "cookbook". I do have some questions:
 Why did you flip the + and  outputs of the "MUX" to the  and + inputs of the "ADC_DelSig"? It shouldn't be a big issue, but you should receive a negative value.
 Have you confirmed that the A, B and C coefficients of your RTD calc component match your PT100 sensor?
Based on a standard PT100 table, the resistance difference between 25C and 85C is 23 ohms. This is a significant error.
Len
"Engineering is an Art. The Art of Compromise."
 Mark as New
 Bookmark
 Subscribe
 Mute
 Subscribe to RSS Feed
 Permalink
 Report Inappropriate Content
I did a simple stepbystep test for R_referense = Rx = 100 Ohm:
at line vRef = MeasureRefResVoltage ();
result = 80 mV (LCD_Position (0,0); LCD_PrintU32Number (ADC_DelSig_CountsTo_uVolts (vRef));)
should be 100mV but this is acceptable.
at line rtdRes = GetRTDRes (vRef);
result = 124500 this corresponds to 63.3 degrees and I see it on the display (RTD Temp = 63.30).
There seems to be a problem in the int32 function GetRTDRes (int32 vRef)
possibly function zeroCurrentOffset = GetOffset (); gives the wrong result.
zeroCurrentOffset = 1300 but should be around 13000.
A similar problem was solved in this thread: Calculating RTD sensors
 Mark as New
 Bookmark
 Subscribe
 Mute
 Subscribe to RSS Feed
 Permalink
 Report Inappropriate Content
Try setting a delay for DAC current stabilization in these 3 functions:
int32 MeasureRefResVoltage()
....
/* Configure the IDAC to source 1 mA */
IDAC_SetValue(125);
CyDelay(50);
....
int32 GetRTDRes(int32 vRef)
....
/* Set the IDAC to pass 1 mA */
IDAC_SetValue(125);
CyDelay(50);
....
int32 GetOffset(void)
....
IDAC_SetValue(1);
CyDelay(50);
....
 Mark as New
 Bookmark
 Subscribe
 Mute
 Subscribe to RSS Feed
 Permalink
 Report Inappropriate Content
PSoC® – Temperature Measurement with an RTD AN70698