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Break through 10kohms limit - series 3

10 kohms range is one of dataTaker series 3 measurement limitation, however there is method to pass this limit without even using a parallel resistor depicted on R6 wiring configuration of resistance measurement (DT8x User Manual).

Resistance measurement is obtained by excite a resistance device with current source, then measure the voltage across. Within dataTaker this voltage reading will get converted back to resistance as measurement result.

Default current source to be used for resistance measurement is type I (~ 213 uA). We can back track the same process using voltage channel to get resistance output.

But we will need to get the real excitation current via TEST command:

TEST report generated at 2018/04/04,14:40:45
dataTaker 85 Version 9.18.6291 Flash 2015/08/07 14:28:13    

Product:          DT85LM3-3    
Serial Number:    xxxxxx   

VEXT                  11.9   V
VSYS                  5.50   V   PASS
VLITH (3.6V)          3.60   V   PASS
VDD (3.3V)            3.28   V   PASS
VANA (3.8V)           3.60   V   PASS
VRELAY (3.8V)         3.75   V   PASS

VREF (2.5V)        2500.40  mV   PASS
Ics I              0.21273  mA   PASS
Ics II              2.5672  mA   PASS

As you can see Ics I is 0.21273 mA, since R=V/I we can try to get 1/I value as 4.70079 so we can do multiplication rather than division. Make sure to have mV reading by using attenuator option.

Normal syntax:

1*R(2W,"Resistance~ohms")

Altered syntax to reach beyond 10 kohms:

1*V(I,A,4.7009,"Resistance~ohms")

In theory the limit of this measurement can reach up to 30V or equal to 141 kohms. There is a possible error that coming from Ics I fluctuation but very small as a trade for range extension.

We can use this method for RTD and thermistor measurement as well but obviously conversion to temperature must be performed manually.

Best regards,
Rudy Gunawan

10 kohms range is one of dataTaker series 3 measurement limitation, however there is method to pass this limit without even using a parallel resistor depicted on R6 wiring configuration of resistance measurement (DT8x User Manual). Resistance measurement is obtained by excite a resistance device with current source, then measure the voltage across. Within dataTaker this voltage reading will get converted back to resistance as measurement result. Default current source to be used for resistance measurement is type I (~ 213 uA). We can back track the same process using voltage channel to get resistance output. But we will need to get the real excitation current via TEST command: ```` TEST report generated at 2018/04/04,14:40:45 dataTaker 85 Version 9.18.6291 Flash 2015/08/07 14:28:13 Product: DT85LM3-3 Serial Number: xxxxxx VEXT 11.9 V VSYS 5.50 V PASS VLITH (3.6V) 3.60 V PASS VDD (3.3V) 3.28 V PASS VANA (3.8V) 3.60 V PASS VRELAY (3.8V) 3.75 V PASS VREF (2.5V) 2500.40 mV PASS Ics I 0.21273 mA PASS Ics II 2.5672 mA PASS ```` As you can see Ics I is 0.21273 mA, since R=V/I we can try to get 1/I value as 4.70079 so we can do multiplication rather than division. Make sure to have mV reading by using attenuator option. Normal syntax: ```` 1*R(2W,"Resistance~ohms") ```` Altered syntax to reach beyond 10 kohms: ```` 1*V(I,A,4.7009,"Resistance~ohms") ```` In theory the limit of this measurement can reach up to 30V or equal to 141 kohms. There is a possible error that coming from Ics I fluctuation but very small as a trade for range extension. We can use this method for RTD and thermistor measurement as well but obviously conversion to temperature must be performed manually. Best regards, Rudy Gunawan
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