Voltage measurement

The EPP3356-0022 principally offers a 2-channel voltage measurement on one box with two very different measuring ranges of ±25 mV and ±12 V nominal voltage. The load on the one connected strain gauge can be calculated from the two simultaneously measured voltages; the EPP3356-0022 already performs this calculation in the box and thus represents a 1-channel box in the sense of load calculation.

The following applies to the individual channels:

• Channel 1:
• Typical measuring range approx. -13.5 V to 0 to +13.5 V (equivalent to process value 0x80.00.00.00 to 0 to 0x7F.FF.FF.FF)
• Nominal measuring range: -12 V... 0 ... +12 V
• max. permissible voltage -U_D vs. +U_D: ±13.5 V
• Measuring error < ±0.1 % of the full scale value, 50 Hz filter active
• Channel 2:
• Typical measuring range approx. -27 mV to 0 to +27 mV (equivalent to process value 0x80.00.00.00 to 0 to 0x7F.FF.FF.FF)
• Nominal measuring range: -25 mV... 0 ... +25 mV
• max. permissible voltage -U_ref vs. +U_ref: ±27 mV
• Measuring error < ±0.1 % of the full scale value, 50 Hz filter active
• in strain gauge mode the connected strain gauge guarantees that no impermissibly high potential differences arise inside and outside the circuit.

In the standard setting the EPP3356-0022 operates as a 1-channel strain gauge monitor with the process image; the box can be switched to 2-channel voltage measurement by changing the process data. See the notes on the process image regarding this. If the EPP3356-0022 is not used as a load measuring box, but rather as a 2-channel analog input measuring box, the following must be observed:

• The CoE settings are to be found for:
• Channel 1: objects under 0x8010:xx
• Channel 2: objects under 0x8020:xx
• the strain gauge objects under x8000:xx have no function. Exception: the averager (0x8000:03) can also be used in voltage measuring mode and applies to both channels simultaneously.
• Self-calibration is not possible and useful.
• The two analog channels are not calibrated by the manufacturer, since this is not required for the relative measurement in strain gauge mode. This means, for example, for channel 1 with a nominal measuring range of ±12 V or a typical measuring range of ±13.5 V, that the maximum measured value 0x7F.FF.FF.FF can be output by one box for example as 13.4 V and by another as 13.6 V. If several EPP3356-0022 are to output identical process values for identical applied voltages, meaning that they are exchangeable, each channel must be calibrated by the user by making settings for each channel in the CoE. The user calibration (CoE 0x80n0:17 [offset], 0x80n0:18 [gain]) or the user scaling (CoE 0x80n0:11 [offset], 0x80n0:12 [gain]) can be used for this.

Voltage measurement In the voltage measuring mode the EL3356 is to be connected to external GND with a single-ended connection. In addition the internal GND reference is to be closed by the CoE switch SymmetricReferencePotential. The EPP3356-0022 “supply” is not usable because the box internally generated 10 V.