| ??? 01/10/05 19:20 Read: times |
#84690 - more details Responding to: ???'s previous message |
Hi Peter.
Peter Herbst said:
Hi Steve
Do I get you right you heat and cool with one element? Yes and no, we couple to the device under test with a Peltier cell, but the back of THAT cell is sitting on a directly refrigerated cooler- compressor and cfc based. And your real problem is tolerance +/-0.05°C ? Not really, we can get that kind of stability (actually we manage +/-0.03 deg stability, but around 0.05 accuracy. What sensor do you use ? Precision calibrated thermistors. How is it connected to the cell? Maby a second sensor on the other side of the Peltier cell might help? Did you check respons time? We actually have three thermistors,one on the refrigerator side, one as close to the cooled surface of the peltier as possible, and one deepdown in the process, around 25mm from the Peltier. Take care Peltier elements are absolutly not linear. We are going to servo these things with a programmable current source this time.previosuly we have used a cascade control with an analogue internal temperature loop servoing on the thermistor closest to the Peltier, and a second digital loop servoing on the inner, core thermistor. Everything is open to suggestions, since the system is essentially back to prototype. BTW We have added about 50W of pure heating to the cooled block to increase the warm up time, since there was no other source of energy other than the joule heating in the Peltier cell when the system is set to warm up. Steve |
| Topic | Author | Date |
| OT Step responses | 01/01/70 00:00 | |
| Step respons | 01/01/70 00:00 | |
| Happy with PID | 01/01/70 00:00 | |
| Re Happy with PID | 01/01/70 00:00 | |
| more details | 01/01/70 00:00 | |
| Making Use of Three Sensors | 01/01/70 00:00 | |
| Heat pipe? | 01/01/70 00:00 | |
| Minimizing Settling Time | 01/01/70 00:00 | |
| Timing | 01/01/70 00:00 | |
| Heat Transfer Rates and Efficiency | 01/01/70 00:00 | |
| Nice estimation | 01/01/70 00:00 | |
| Worked that out | 01/01/70 00:00 | |
| Segments of different PID parameters | 01/01/70 00:00 | |
| integrating cap | 01/01/70 00:00 | |
| Abruptly changing... | 01/01/70 00:00 | |
| Exaclty | 01/01/70 00:00 | |
| Have you Read Above? | 01/01/70 00:00 | |
| Sorry | 01/01/70 00:00 | |
| Maybe this can help? | 01/01/70 00:00 | |
| Interesting | 01/01/70 00:00 | |
| Reference | 01/01/70 00:00 | |
RE: Reference | 01/01/70 00:00 |