Navigation:  Tutorials > Measurement tutorials > Voltage and current > DEWESoft 7.0  data acquisition, processing, analyzing and storage software Channel setup

Let's take a look at how to make the DEWESoft setup for the configuration shown on the previous picture. There are three Dewetron programmable modules - one for high voltage DAQP-DMM (could also be a new DAQP-HV) and two voltage modules DAQP-V .

 

Since the input voltage of DAQP-DMM is ±1000 V, the voltage can be measured directly without any of additional transducers. We set the voltage range to 400 V, since 230 Vrms · sqrt(2) = 325 V peak.

We need to take special care for the settings of the Lowpass filter . If this setting is lower than half of the sample rate, it will cut the signals already in the range of the measurements. Sometimes this is needed, but more often this filter is set to the low range by mistake, and then the measurement results will be invalid.

 

Now let's calibrate the current. Below is the picture from the current clamp sensor.

 

Since we have only the light bulb, 10 A Range will be more than enough. It is very important that the measurement range is chosen according to the expected signal. If we choose too high of a range, the inaccuracy of the current clamps will be too high to produce correct readings. At this range, the sensitivity of the sensor will be 1mV/mA, which means that 1 mA at input will output 1 mV at the output. In the channel setup we enter that the measurement of current I is in unit A, and leaving the scaling factor as 1. That’s all there is to this one. Let's take a look how to scale the shunt resistor.

There is an easier way to scale the shunt resistor - which will be covered later, but let's look at the theory of how to scale the shunt resistor. This is a 0.1 Ohm shunt. Since it is connected in sequence, the current will be the same on all elements. The voltage drop will be measured on the shunt resistor. From the Ohmic law, the current for the voltage drop is calculated as follows:

U = R · I = 0.1 I

So, there will be 0.1 V at the output for 1 A current or 1 V for 10 A.

It is time to enter the scaling factor. We enter the unit of measurement as A . Then we go to the second point scaling and enters that 1 V measured equals 10 A . That's all.

 

Channel setup for channel 2 - Current2

We also have an additional option to define the shunt type. For sensors with current output, it might happen that the current is only the transfer mechanism and the real measurement value is different (like pressure). There, we would need to combine scaling factors from real measurement (pressure) to current, and then from current to voltage.

Therefore, it is convenient to define the shunt resistor as the part of the amplifier. In the section of the amplifier, we can define the shunt type. Standard Shunt1 is a precise 50 Ohm resistor, used to measure 4÷20 mA or 0÷20 mA current loops. The shunt 2 is 0.1 Ohm resistor, used to measure currents up to 5 Amps.

We will learn how to use the shunt resistors in the next tutorial → Sensors with voltage/current/digital outputs