GoldExI : FAQ : Measure V(T)

Question

How to measure Voltage vs. Temperature i.e. V(T)?

Answer

This kind of measurement is carried out in semi-automatic fashion. After pressing "Do It" button you should slowly change the temperature of the system while GoldExI measures one or several voltages and monitors the temperature. Thus you get V1(T), V2(T), etc..

To make this measurement it is necessary to define at least one positive or negative virtual voltage and a virtual voltage which will be used for temperature sensing (t-sensor). This can be defined in Options|Virtual Voltages or directly from Measurement window by clicking the button next to proper virtual voltage indicator.

The number of points on the final V(T) dependence can be specified in the special field of the Measurement window. The time interval between consequent measurements can be set in Options|V(T). There, you can also set the minimum difference of temperature between consequently measured data points.

Sometimes measured voltage is affected by thermo-EMF (Electro-Motive Force) which always exists in the contacts of your measurement circuit. GoldExI allows you to compensate for this, by switching on [x] "Anti Thermo-EMF" feature in V(T) Options. In this case GoldExI assumes that the current which passes through your sample (and which causes voltage drop) is a Sweep1 current defined in GoldExI. So, GoldExI will measure V for positive and negative directions of sweep1 and find an average value, thus getting rid of thermo-EMF. To allow measured voltage to relax after abrupt change of current sign, GoldExI introduces the standard delay between "Set Current and GetVoltage" which can be set in Options|Delays.

Often one needs to measure the resistance vs. temperature i.e. R(T) instead of V(T). The R(T) mode can be activated [x] in V(T) Options window. To calculate R GoldExI needs to know the current, so it assumes that the current through the circuit is the virtual current defined as sweep1. Note, that you can use R(T) and Anti-Thermo-EMF mode in the same time.

After each measurement, V(T) Options window shows a statistics of errors during the last measurement run. When one of the errors happens during measurements, you will here a click. The following errors are possible:

not possible to get temperature. This can be e.g. because temperature sensor voltage/resistance is outside interpolation table loaded by you. see Options|Thermometer Setup .
measured temperature is too close to the previous value. The measurement was skipped.
in R(T) mode GoldExI was going to divide by zero. The measurement was skipped.

If, after pressing "Do It", you hear only clicks and measurement process does not go on, you may interrupt it (pressing Escape) and check statistics. It will point out were the problem is.