Analog Output Option
Features
- 0-20 mA or 4-20 mA plus 0-10 Vdc
- 0.025% resolution
- Isolation to 250 Vac
- Outputs linearized to reading
- Scale and offset via RS232, RS485, or front panel
- 56/s update rate at 60 Hz power, 47/s at 50 Hz power
- 12 V compliance at 20 mA
- Output derived from filtered or unfiltered signal input
Description
The Micro analog output option board provides an isolated 0-10 Vdc voltage signal to drive a chart recorder, plus an isolated 0-20 mA or 4-20 mA current signal for transmission to a computer or central control room. This option is compatible with all Micro meters and counters, and turns these into highly accurate, sourcing, 4-wire transmitters. The output for thermocouples, RTDs and custom curves is linearized to the displayed reading.
A 12-bit D-to-A converter provides .025% resolution. The update rate is a fast 56/s at 60 Hz power or 47/s at 50 Hz power. The analog output can track the unfiltered signal for fastest response, or the digitally filtered signal for best noise rejection.
Scaling of the output is easily entered via front panel pushbuttons or via the serial digital interface. The displayed readings to produce the low and high analog outputs may be set to any value from -99,999 to +99,999 for DPMs, or -999,999 to +999,999 for counters.
Both the current (0-20 mA or 4-20 mA) or voltage ( 0-10 V) outputs are available at the same time, and the same scaling applies to both. The output selected in software is calibrated to 99.9% accuracy. The non-selected output is accurate to 98%.
Isolation is provided by a separate on-board power supply, which is powered by the meter. This supply can drive 20 mA current into loads up to 600 ohms, for 12 V compliance. Isolation to signal ground and power ground eliminates problems caused by ground loops.
The addition of the analog output option turns Micro temperature meters into superb, isolated, linearized, 4-20 mA temperature transmitters with exceptional accuracy and high-speed response.
Specifications
| Electrical | |
| Power Source | Provided by meter |
| Signal Source | Filtered or unfiltered digitized signal |
| Output Linearization | Linearized to display |
| Output Levels | ( 0-20 mA or 4-20 mA ) and 0-10 Vdc |
| Compliance, 0-20 mA | 12 V ( 0-600 ohm load ) |
| Compliance, 0-10 V | 2 mA ( 5 kOhm min load |
| Isolation | Safety-rated to 250 Vac, 4.2 kVp per High Voltage Test |
| Accuracy | 99.9% selected output, 98% non-selected output |
| Output Nonlinearity | <0.05% |
| Output Resolution | 12-bit ( .025% of FS ) |
| Output Update Rate | 56/s at 60 Hz power, 47/s at 50 Hz power |
| Response Time | 17 ms (unfiltered DPM) |
| Gate time + 30 ms + 0-2 periods (counter) |
| Scaling | |
| Zero Output | -99,999 to +99,999 (DPM), -999,999 to +999,999 (counter) |
| Full Scale Output | -99,999 to +99,999 (DPM), -999,999 to +999,999 (counter) |
| Minimum Span | 150 counts |
| J4 Pin Assignments |
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Application Examples
Driving a Strip-chart Recorder
The 0-10 V output capability of the analog output board is ideal to drive a strip chart recorder. As for 4-20 mA, the 0-10 V output can be scaled to the meter reading to highlight signal level changes in a range of interest.
Use as an Isolated, Linearized 4-20 mA Transmitter
0-20 mA output capability turns Micro meters and counters into high-accuracy, high-speed, isolated 4-20 mA transmitters. The output is linearized to the reading, a major benefit with thermocouple and RTD inputs.
The 4-20 mA signal can be transmitted via twisted pair wires to a control room for supervisory process monitoring and control. Process meters in series with the signal can provide local readouts in engineering units where required.