3-wire system
In principle, these measuring amplifiers operate similarly to the 4-wire system, but with one less wire.The 3-wire system records the fault due to one current feed using only one additional "voltage" wire, and adjusts this from the raw measuring value twice. The only differences from the 4-wire system are that the built-in electronics are more complicated, and that the three wires need to be the same material and length.
In theory, it is possible to have very long sensor leads with these systems. Nevertheless they are restricted by the effects of interference (EMF), for example. Shielding is strongly recommended and possibly even double shields for longer lines. In this respect, the 4-wire system is easily superior.
 [Schematic] |
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 |
Output | ||
| Range | 0...10V | 0...20mA | 4...20mA |
| -50C...+50C | 57.805.9753.0 | 57.805.9853.0 | 57.805.9253.0 |
| 0C...+100C | 57.805.2953.0 | 57.805.3053.0 | 57.805.3153.0 |
| 0C...+150C | 57.805.5153.0 | 57.805.5253.0 | 57.805.5353.0 |
| 0C...+200C | 57.805.6053.0 | 57.805.6153.0 | 57.805.6253.0 |
| 0C...+300C | 57.805.6953.0 | 57.805.7053.0 | 57.805.7153.0 |
| 0C...+400C | 57.805.7853.0 | 57.805.7953.0 | 57.805.8053.0 |
| 0C...+500C | 57.805.3353.0 | 57.805.3453.0 | 57.805.3553.0 |
| Technical Data | |
||
| Supply voltage | 24 V +/-20% | ||
| Power consumption without output current | ca. 12mA | ||
| Polarization of supply voltage | Diode | ||
| Sensor | Pt 100 DIN IEC 751 | ||
| Measuring current | ca. 2mA | ||
| Interference suppression at sensor | RF-filter | ||
| Basic error at 20C typ. | 0.2% v.E. | ||
| Total errors w/o temp. limits | 0.5% v.E. | ||
| Load error (add.) at current output | 0.02%/100ohm | ||
| Rated load impedance at current output | 100ohm | ||
| Output | |
||
| Internal res. with standard voltage/current | Ri=100ohm/>5Mohm | ||
| Max. load at current output | 500ohm | ||
| Output prot. against interference voltage | Z-Diode | ||
| Temperature Limits | |
||
| Operating temp. | 0C...+50C | ||
| Horizontal mount, 2 cm. | 0C...60C | ||
| Storage temp. | -40C...+85C | ||
4-wire RTD to analog convertors
Measuring amplifier
Measuring amplifiers produce linear standard signals, from sensor signals, which are usually small, non-linear and zero-displaced.Pt 100 describes a standardized calibrated resistance element of platinum wire which has exactly 100 ohms at 0 degrees C, and consistently changes its resistance value within temperature limits (approx. 0.4ohms.K). Unfortunately this sensor is not linear, so linerization needs to be performed.
There are several ways to connect this sensor to the measuring amplifier, e.g. 2-, 3- and 4-wire connection. For the first time, Wieland is no longer producing the 2-wire system, because measuring value corruption can quickly increase over longer lines.
4-wire system
The problem of measuring innaccuracies is completely eliminated with the classic 4-wire system as two additional wires pick up the voltage drop directly at the sensor and feed it back for evaluation.
 [Schematic] |
|||
|
Output | ||
| Range | 0...10V | 0...20mA | 4...20mA |
| -50C...+50C | 57.805.8153.0 | 57.805.8253.0 | 57.805.9153.0 |
| 0C...+100C | 57.805.1753.0 | 57.805.1853.0 | 57.805.1953.0 |
| 0C...+150C | 57.805.4853.0 | 57.805.4953.0 | 57.805.5053.0 |
| 0C...+200C | 57.805.5753.0 | 57.805.5853.0 | 57.805.5953.0 |
| 0C...+300C | 57.805.6653.0 | 57.805.6753.0 | 57.805.6853.0 |
| 0C...+400C | 57.805.7553.0 | 57.805.7653.0 | 57.805.7753.0 |
| 0C...+500C | 57.805.2153.0 | 57.805.2253.0 | 57.805.2353.0 |
| Technical Data | |
||
| Supply voltage | 24 V +/-20% | ||
| Power consumption without output current | ca. 12mA | ||
| Polarization of supply voltage | Diode | ||
| Sensor | Pt 100 DIN IEC 751 | ||
| Measuring current | ca. 2mA | ||
| Interference suppression at sensor | RF-filter | ||
| Basic error at 20C typ. | 0.2% v.E. | ||
| Total errors w/o temp. limits | 0.5% v.E. | ||
| Load error (add.) at current output | 0.02%/100ohm | ||
| Rated load impedance at current output | 100ohm | ||
| Output | |
||
| Internal res. with standard voltage/current | Ri=100ohm/>5Mohm | ||
| Max. load at current output | 500ohm | ||
| Output prot. against interference voltage | Z-Diode | ||
| Temperature Limits | |
||
| Operating temp. | 0C...+50C | ||
| Horizontal mount, 2 cm. | 0C...60C | ||
| Storage temp. | -40C...+85C | ||
How to contact us: Wieland may be contacted by calling us at: 1-800-WIELAND
or by email at: sales@wielandinc.com
©1996 Wieland, Inc.
49 International Rd.
Burgaw, NC 28425
comments to: sales@wielandinc.com