SfAR - FAQ
Q: Is an external power supply needed to activate the DI input in SFAR modules? Is it enough to connect IN to COM?
The voltage must be applied to the digital input. Shorting the IN input with GND is not enough. The pulse parameters should be as follows:
• low state "0": 0 - 3V
• high state "1": 6 - 36V
You can use the voltage from the module power supply while losing the optoisolation between the communication path and inputs. In the absence of optoisolation, when high voltage appears at the input of the module, the voltage will also appear on the entire bus, damaging the other SFAR modules and probably the driver supporting the bus.
Q: What is the maximum load current of the output (single channel) in MOD-8I8O and MOD-16O-PNP?
The load is 500mA per single channel.
Q: Can SFAR-S-16DI have AC inputs?
Digital inputs are for connecting an AC signal. However, due to the fact that these inputs are fast and allow to count pulses at a frequency of 1 kHz, it is not possible to use them to monitor the presence of a variable frequency signal, e.g. 50 Hz, because depending on the moment when the input state occurs, reading With the Modbus protocol, we can get different results even though the AC voltage is still present. To be able to monitor AC signals, we have introduced the ability to filter digital inputs. The filtration works in such a way that a high state occurs when the voltage is held for at least 40 ms. Low occurs when there is no voltage for at least 80 ms. The filter can be turned on independently for each input of the device using register 40018.
Q: Can I use SFAR-S-6TI for one PT100 sensor and DI input on an SFAR module?
The SFAR 6TI module can use one input for the PT100. Regarding the second input, you can create an application in the controller that will use resistance measurement, e.g .:
for the measurement of 8084 Ohm, it will act as digital 1
for 0 Ohm the measurement will work as digital 0 (by connecting the input to the ground)
Purchasing SFAR-1M-1TI1DO and SFAR1M-4D will also be a good option.
Q: Are the analog outputs in the SFAR-1M-2DI1AO module galvanically isolated?
Yes, the analog output is galvanically isolated.
Q: What is the input impedance of the voltage input (for the range 0-256mV)?
The MOD 1TE module input impedance is 100k Ohm.
Q: Can the SFAR-1M-2DI2DO read with a frequency of at least 15 Hz?
Yes, SFAR-1M-2DI2DO will count at 50Hz even with an input filter. The SFAR-1M-2DI2DO inputs can count quickly at 1kHz. Their resolution is 32 bits and they cooperate with PNP and NPN sensors.
Q: Why does the MOD-6TE module not remember the lead resistance parameter? Is this parameter taken into account in the algorithm when selecting a thermocouple?
The MOD-6TE does not save the "Lead resistance" parameter as it would be written to the EEPROM which would damage it. When selecting a thermocouple, this parameter is not taken into account, the temperature of the cold ends is calculated by a sensor mounted inside the module.
Q: Are terminals com1, com2, com3 and com4 in the SDM-16RO module separated from each other?
In the SDM-16RO module, all terminals are separated from each other. According to the specification of the device:
Maximum current 3A 250V AC / on COM,
Maximum current 3A 30V DC / on COM.
Q: The measurement in MOD-6TE module using a thermocouple is inaccurate, what should I do?
When measuring temperature with the use of a thermocouple, the measurement error of the thermocouple itself should be taken into account, which in extreme cases may result in a difference of up to 3 C between the sensors. The temperature of the junction is measured inside the module and is susceptible to external factors, i.e. the location of the module, the time from applying power to the module until the temperature value is read, etc. You can eliminate the error in measuring the temperature of the junction by entering a constant average temperature in which the module is located and in the window configuration of the channel, selecting the "Constant value of connectors' temperature" option.
Q: What are the causes of unequal indications between individual channels when measuring with a thermocouple in the 6TE module?
There is a problem with measuring the cold junction temperature. The temperature of the cold ends is unevenly distributed throughout the module because there are elements that emit heat in the module. The temperature of the cold ends does not have to be close to the ambient temperature of the module, usually, it will be higher due to the heat generated by the module itself and which heats the metal parts of the connector.
Q: How to prevent uneven readings between individual channels when measuring with a thermocouple in the 6TE module?
The best method for very accurate measurements is to place the cold ends in a separate cabinet with no active components and even temperature distribution. Then measure the temperature of cold ends, e.g. with a PT100 sensor connected to one of the channels of the 6TE module. In the next step, build logic in the control unit, which reads the temperature of cold ends and writes it to the module in the "Constant value of connectors' temperature" register.
Q: When configuring the sensor of the 6TE module, it is possible to select the "Constant value of connectors' temperature" option. How does selecting this option affect the measurement?
If the "Constant value of junction temperature" option is selected, the module will use the register value 40081 (R / W) as the cold junction temperature. This can be used when the cold ends are not placed directly against the module, but elsewhere. If this option is not selected, the cold junction temperature value will be read from the register 30061, ie from the cold junction temperature sensors in the module.
Q: When configuring the sensor of the 6TE module, it is possible to enter the "lead resistance" value. What influence does this parameter have on the measurement?
The resistance of the leads applies to a two-wire measurement with a PT100 sensor. The connection of the sensor with the processing electronics is done with a 2-wire cable. Like any other conductor, this cable has an electrical resistance connected in series with the temperature sensor. Thus, two resistances are added and the result is a systematically higher temperature reading. Over longer distances, the resistance of the leads can be many ohms and create a significant shift in the measured value. In such a situation, enter the Lead resistance parameter to correct a possible measurement error. The value of this parameter is not saved in the EEPROM memory, so it is best to write it to the appropriate register using the superior driver. If the PT100 sensor is 3-wire, this parameter is calculated.
Q: Can we use SFAR-S-6TI for one PT100 and one digital input is working on the SFAR module?
A: In the SFAR 6TI module you can use one input for PT100. Regarding the second input you can create an application in the controller which will be use resistance measurement e.g.:
for 8084 Ohm measurement will be working as a digital 1
for 0 Ohm measurement will be working work as a digital 0 (by connecting the input to ground)
Purchasing SFAR-1M-1TI1DO and SFAR1M-4D will be a good solution too.
Q: Can SFAR-S-16DI take AC inputs?
Digital inputs allow connection of the AC signal. However, since these inputs are fast and allow counting pulses at 1 kHz frequency, it is not possible to use them to monitor the presence of a variable frequency signal like 50Hz because, depending on the moment at which the input state is read with the Modbus protocol, we can obtain different results even though AC voltage is still present. To be able to monitor the AC signals, we introduced the possibility of filtering the digital inputs. Filtration works in a way that the high state occurs if the voltage is maintained for at least 40 ms. The low state appears when there is no voltage for at least 80 ms. The filter can be turned on for each input of the device independently using the 40018 registers.
Q: Can SFAR-1M-2DI2DO read with at least 15Hz?
Yes, SFAR-1M-2DI2DO even after using input filter will count with 50Hz frequency. SFAR-1M-2DI2DO inputs can fast count with 1kHz frequency. Their resolution is 32bits, and they work with PNP and NPN sensors.