4 AO HART for ET200iSP in hazardous areas
The Siemens 6ES7135-7TD00-0AB0 is a SIMATIC DP electronic module for the ET200iSP distributed I/O system, providing 4 analog outputs with HART protocol support for connecting HART field devices in hazardous-area installations. It carries Ex ib (ia Ga) IIC T4 Gb, Ex ib [ia IIIC Da] IIC T4 Gb, and Ex ib [ia] I Mb approvals.
Output performance and loop drive
Each of the 4 channels outputs 4 mA to 20 mA (also supports 0 to 20 mA) into a maximum load of 750 Ω with current outputs — enough to drive a typical HART transmitter or I/P positioner plus cable resistance in a long loop. Resolution is 14 bit including sign, with a linearity error of ±0.015 % and a repeat accuracy of ±0.01 % at 25 °C, so the loop stays tight for custody-transfer or critical process control. Crosstalk between outputs is better than -50 dB, which means a step change on one channel won't couple into an adjacent loop and upset a sensitive control valve. The module detects wire-break and short-circuit conditions on each output, and reports diagnostic alarms via the backplane bus — the SF (red) group error LED gives the panel operator a visual cue before the process drifts.
Panel fit and power budget
The module measures 30 mm wide × 129 mm high × 136.5 mm deep, fitting a standard ET200iSP slot in the hazardous-area I/O cabinet. Typical power loss is 2.7 W, and it draws 295 mA from the backplane bus — well within the power budget of an ET200iSP interface module. Maximum cycle time across all 4 channels is 3.6 ms, fast enough for most process control loops; the module supports substitute values if communication to the DP master is lost, so the last good output value holds the process steady.