Uninterrupted power supply

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The problem with uninterrupted power supply divides in some sections:

1 UPS functional type Online UPS means, that the output-power ist constantly generated from the battery while the battery becomes constantly loaded from mains power. This concept ensures uninterrupted output-power even in the moment of mains powerfail. Other concepts deliver mainspower and start generation from battery only in case of powerfail. The startup of generation may take some (short) time. So the output-power can have dips or other deformations in the moment of powerfail, which could cause the "load" instruments to stop working.

Choose a high-quality UPS with "online"-generation.

2 UPS output voltage: The waveform should be sinewave or stepped approximation to sinewave. The voltage should meet the Oxy-requirements which are 110 or 230V at 50 or 60 Hz with serie A-D according to the setting at the Oxygraph mains input. Serie E and F accept nominal voltages from 100 to 240 V 47 - 63 Hz, due to accepted tolerances of +/- 10 % the maximum range covers 90 - 264 V.

For the waveform of any UPS is only "close" to a sinewave its always a good idea to stay securely within these ranges and not to explore the boundaries. The type of "rectangle"-output UPS and most cheap UPS come with the risk of interference with the loads electronics.

3 UPS Output maximum current: The instruments powered by the UPS draw different currents at startup, at running with full load or in normal operation. The UPS needs to limit the current to prevent its internal electronics from damage. This limitation may cause problems with the "load" instruments especially at startup when they need to switch on transformers or to load capacitors, thus drawing inrush-currents.

Therefore an UPS with inrush capability is preferable.

4 UPS Output thermal current: The output current will warm up the internal electronics of the UPS, which is designed for a certain maximum of continuous current. All "load"-Instruments together may not reach this value during an experiment.

So the rated UPS output continuous current has to be higher then the sum of continuous current of all connected instruments, including Oxygraphs, computers, monitors.

5 UPS power failure buffering time The battery of the UPS in normal operation is fully charged by the mains supply, the batteries capacity becomes only relevant in case of mains powerfail. From fail on the battery has to deliver all the energy used by the load. The longer an experiment should be continued without mains power the bigger batteries must be used.

Calculate more power failure buffering time than you ever plan to use. The battery will loose capacity during lifetime and the convenient use will increase the number of "load" Instruments.

Oxygraph power-consumption Serie E, F: nominal mains input: 100 - 240 V 47 - 63 Hz maximum mains range: 90 - 264 V inrush-current: depends on the mains power net impedance, at WGT-Labs we measured maximum 45 A for 5µs. With limited current the inrush becomes lower in current but takes more time. We measured 8A for 50 µs. maximum current: At ambient temperature 25 °C with Chamber temperature set to 0° the Oxygraph takes full peltier-power. Additionally the stirrers and the TIP moving will add to a maximum of 110 W and 0,5 A at 50 Hz. normal operation: 25 ° C ambient and 37° C chamber lead to app. -11% peltier-power thus consuming 40 W from mains power. 25 ° C ambient and 5°C chamber lead to ca. -66% peltier-power thus consuming 75 W from mains power.

I use "load" instrument for all electric equipment connected to the UPS.

Even cheap UPS may work properly. Even the most luxury UPS still can cause some complications with certain load-situations.

We can not guarantee functionality of UPS-powering of Oxygraphs. If all the above mentioned criteria are carefully attended to we suppose experimental equipement will serve smoothly.