[deutsch]

communicating thermo electric temperature controller

The successful product has continously been improved. The current TEC is again a OEM product to be built into your machinery where it controls the temperature standalone and yet lets the user do interactive adjustments when required.


Features a closer look at the OEM product
  • Linear, dissipating H-Bridge design
  • single power supply 5.2V to 15V DC, 20mA while standby and communicating
  • current capability few Amps, the semiconductors allow > 10A, limited by heat dissipation
  • communicates to a PC either through RS232 or RS422
  • Temperature is preset by software, a potentiometer is optional
  • Temperature stability down to 0.005 Deg C when using RS422, somewhat less with RS232
  • absolute accuracy is not yet specified, but wil be in the order of 2 degrees.
  • Easy to use Windows user interface to control and monitor is included
  • Runs standalone, without PC connection, on a fixed temperature
  • communication commandset is available for download
  • Fast PID controller with 16 bit of precision
  • Protected against active and passive side over temperature, overcurrent, sensor failure and reverse supply
  • Latching fault behaviour, requires power on/off or communication to unlatch
  • two 1% NTC temperature sensors are included, but PT1000 are possible.
  • Settable userdefined string lets the user distinguish multiple TECs on a bus
  • pcb size 90 x 62 x 20 mm (width x depth x height)
  • standard heat sink included, 110 x 80 x 50 mm
  • Manufactured according to the european RoHS regulations
  • Fullfills the relavant CE norms EN 60950-1, EN 61010-1, EN 61000-6-2, EN 61000-6-4
image of semi product to be built inside your designs, here shown with included heatsink, mechanical drawings are available

A look at the lab grade RS232 to RS422 converter :
image of RS232 to RS422 converter


Possibly repeating what has been said, there is a TEC manual

FAQ

What kind of power supply is recommended ?

For top accuracy a linear supply, but a switching power supply is possible at somewhat degraded accuracy.

Why is there less accuracy with RS232 ?

EMI compliance requires all lines to be RF-shorted with caps to Earth. When the Earth is (as usual) not connected, the single ended RS232 couples to the sensor lines, while the lower voltage RS422 differential lines do not couple.

Why is there a difference in stability and absolute accuracy ?

Absolute accuracy means any TEC out of the box with any of the supplied NTC sensors is as accurate as specified. Stability on the other hand, means the preset temperature is held constant to the specified margin.
This TEC is able to work with PT1000 which is (by the physics and manufacturing) having an absolute accuracy of in the order of 0.15 or 0.25 degrees. A special 4 wire connection to the PT1000 is provided.

should I use the NTC or rather a PT1000 ?

The slope of the NTC is much steeper, thus the achieveable stability of the NTC is higher. On the other hand when the sensors are to be replaceable, the PT1000 are tighter specified and the absolute accuracy better. The measurement of the resistor pair (temperature variable and fixed) is radiometric and is thus almost independent on the supply stability and accuracy. Nevertheless a 25ppm/K 2.5V reference is used as source for the temperature divider. Some calculated data.

NTC : ADC counts per degree vs temperature PT1000 : ADC counts per degree vs temperature

As can be seen, the resolution of the PT1k measurement is less than an order of magnitude lower than the measurement of the NTC. The temperature stability is limited to 1 bit of the control loop, moreless. Thus the NTC stability is in the order of 2mK (500 counts per degree) and the PT1k stability is in the order of 50mK (20 counts per degree).
Ahem. The built in reference resistor has an accuracy of 1% and a temperature coefficient of 100ppm/K. A precision resistor with an accuracy of 0.01% and a temperature coefficient of 2ppm/K is available for approximately 10 Euros. The pcb is prepared for mounting it. An error calculation has not yet been done.


A brief look at the included Windows GUI. The current version is improved in the versatility. It can control 2 channels at once and displays temperatures in a floating point format.

The different pages of the pageview What it does
first page of pageview The dual view is available with the menu top left. Default is the single channel view.

This first page shows the communication state of the PC and the TEC plus some fixed standard data. It also supports to control multiple TEC on a RS422 bus. Each TEC has an own user defineable string which can be read and written here. It even allows for some command debugging for those writing their own software.

In the example here, we have current model (2006) to the left and an older model (2004) to the right.
second page of pageview The second page contains static setup data, vital for the correct function. Both sides of the Peltier are to be kept within settable limits. Since the TEC itself operates with integer arithmetic, it supplies the necessary floating point multipliers for the GUI to let the user operate with floating point numbers.
third page of pageview The third page contains dynamic data and show how the loop operates. It allows to optimize the loop parameters. Several values of interest can be set to be visualized in a scaleable graph.

Note that at equal scalings of 0.01 degree per grid unit, the 2006 model has a stability of far below one unit, while the 2004 model has very infrequent steps of 0.01 degrees, which appears to be the measurement resolution. One could now compare the RMS deviation of the two. It should be added that the right setup runs in an extremely well isolated box, while the left runs unshielded.

Shipment

Shipment includes matching power/sense connector, two 1% 10k NTCs for either side of the peltier, the pcb is mounted on a heatsink as shown in the picture above. Also included is a flatribbon cable with a DSUB-9 RS232 connector. Not included is the RS422 converter.
Prices without VAT.

Pricing @ 1 @ 10 @ 50
CHFr 398.90 363.20 331.10
Euro approx 332 303 276
USD approx 499 454 414

Based on 1 Euro = 1.20CHFr, 1 USD = 0.80CHFr, Sept 2011


Available on additional charge Optional Savings

products page
ibrt home page

last update 24.sept.2011 or perhaps later

Copyright ibrt (1999-2011)