rEvodream is all independent electronic system that informs the diver about oxygen partial pressure in the breathing loop. For easy use, rEvodream is attached, with titan housing, to oxygen and/or dilluent pressure gauge. rEvodream can display ppO2 read out from one or two sensors. When two sesnsors are connected and correctly calibrated, rEvodream displays ppO2 from both sesnsors alternatively, in 3 seconds intervals. 

rEvodream P5 consist of:

- ppO2 display with battery and measuring electronics
- HUD with the wire
- wires for oxygen sesnsors - at the end of each wire there are 2 molex connectors for 2 sensors

SWITCHING rEvodream ON AND OFF

To switch rEvodream on press once (1P - "one push") piezo button on ppO2 display. After start-up, rEvodream HUD informs how many calibrated sessors are attached. This information is provided by LED sequence: orange > green > red. If two correctly calibrated sensors are ocnnected to rEvodream, the squence is displayed twice. If there's only one sensor - the squence is displayed once. After that rEvodream starts to display ppO2.

rEvodream can be switched off in 3 following ways:

1. By pressing piezo button once (1P) in within 2 minutes from switching it on
2. By pressing piezo button once (1P) if ppO2 < 0.5 bar (in this condition time doesn't matter)
3. Automatically, if ppO2 <= 0.25 bar for 15 minutes

CALIBRATION

Before we discuss rEvodream calibration, it should be mentioned, that calibration is a process of "teaching" the electronics, what voltage the sensor generates at known ppO2 (see "Sensor calibration" article). When rEvodream is in CCR mode, it assumes that the sensor is surrounded with 100% oxygen during calibration. Unlike Shearewater, rEvodream doesn't have atmospheric pressure sensor, so during calibration it assumes that ambient pressure is 1.0 bar. As we know, ppO2 is the product of oxygen fraction and ambient pressure, so during calibration reVodream measures voltage of the sensor at 1.00 bar ppO2. That makes the basis for calculating higher ppO2 during the dive. 

Example:

During calibtration the sensor voltage was 50 mV, so ppO2 1.00 bar = 50 mV

During the dive this sensor generates voltage of 65 mV, what rEvodream reads as ppO2 = 1.30 bar (65/50=1.3)

rEvodream calibration should be preceded by full oxygen flush. After flushing the loop with oxygen, you can start calibration pressing piezo button 3 times (3P), when rEvodream is switched on. The calibration process proceeds as follows:

1. First, the sensors' voltage is displayed and according to these values sensors wlle be calibrated or not:

• if the voltage of the first sensor is in correct range (36 - 64 mV), this sensor will be calibrated 
• rEvodream sets ppO2 = 0,99 on the display and HUD's green LED flashes few times, confirming successful calibration and calibration of the second sensor starts
• if the voltage of the first sensor is lower than 36 mV, rEvodream assumes that sensor is failed and sitches it off. HUD's orange LED flashes few times, confirming failed calibration and calibration of the second sensor starts
• if the voltage of the first sensor is higher than 64 mV, rEvodream assumes that sensor is failed and sitches it off. HUD's red LED flashes few times, confirming failed calibration and calibration of the second sensor starts

2. If at least one sensor is successfully calibrated, rEvodream asks about altitude calibration (see next section), by flashing all 3 LEDs twice. To confirm altitude calibration mode you should press piezo button once (1P). rEvodream confirms entering altitude calibration mode by HUD LED sequence orange > green > red. Now you can correct ppO2 of the calibration. You can read more about altitude calibration in the next section of this article.

3. If none of the sensors can be calibrated, rEvodream shows that with rapid alternate flashing of red and orange HUD LEDs and then switches off. From this moment rEvodream won't operate and every try of switching it on will end with information about failed calibration (rapid alternate flashing of red and orange LEDs) and switching it off, untill at least one oxygen sensor of rEvodream will be correctly calibrated. After solving problem with the sensors you should repeat calibration. 

ALTITUDE CALIBRATION

As mentioned before, during calibration in CCR mode, rEvodream assumes that ambient pressure is 1.00 bar and 100% oxygen in the breathing loop. These criteria are fulfilled rather rarely in practice. Ambient pressure can be lower or higher than 1.00 bar and oxygen content in the loop is not always 100%. The example of such situation can be altitude diving with atmospheric pressure below 900 mbar (0.9 bar) or using oxygen of purity lesser than 100% (95% - 96%). Let's say - for example - that atmospheric pressure is 970 mbar (0.97 bar) and oxygen percentage in oxygen tank is 98%. In that case real oxygen partial pressure after flushing the loop is 0.97*0.98 = 0.95 bar. And that value will be shown after calibration by Shearewater. If you don't change rEvodream calibration, it will show ppO2 = 1.00 bar, so there'll be 0.05 bar difference between Shearewaterem and rEvodream. 

To avoid such situation you can use "altitude calibration" mode. After succesfull calibration, rEvodream asks about altitude calibration, by flashing all 3 LEDs twice. If you want to enter altitude calibration mode to change calibrated ppO2, press piezo button once (1P). rEvodream confirms entering altitude calibration mode by HUD LED sequence orange > green > red. Now you can correct ppO2 using piezo button - pressing Piezo you reduce ppO2 value displayed. When you reach correct value just wait - after 2 seconds rEvodream saves corrected ppO2 and goes to standard working mode. Saving of any change is always confirmed by green LED rapid flashing.

rEvodream MODES

Although in most cases you will use rEvodream in standard mode, you should know about its additional features. 

CCR MODE (default)

In CCR mode rEvodream assumes that sensors were calibrated with 100% oxygen at 1 bar ambient pressure. Default HUD ppO2 display mode is "rEvo 1.30 PPO2 green zone". In this mode desired ppO2 is 1.30 bar so when it ranges from 1.25 to 1.40 only green HUD LED is on, constantly (everything is OK). The variations of PPO2 are symbolized as follows:

PO2 < 0,3 orange LED flashes rapidly
> 0,3 < 0,5 orange LED flashes twice for every 3 seconds
> 0,5 < 0,7 1 long pulse of orange LED for every 3 seconds + green LED constantly on
> 0,7 < 1,0 1 short pulse of orange LED + green LED constantly on
> 1,0 < 1,25 1 very short pulse of orange LED + green LED  constantly on
> 1,25 < 1,40 green LED constantly on
> 1,40 < 1,45 1 very short pulse of red LED for every 3 seconds + green LED constantly on
> 1,45 < 1,55 1 pulse of red LED for every 3 seconds + green LED constantly on
> 1,55 < 1,65 2 pulses of red LED for every 3 seconds
> 1,65 red LED flashes rapidly

Alternative HUD ppO2 display mode is "rEvo 1.0 pulse code". When PPO2 = 1,0 only green LED is constantly on

For every 0.1 bar above 1.0, the red LED will pulse once. (up to 1.5 bar).
For every 0.1 bar below 1.0, the orange LED will pulse once.

Below 0.5 bar, the green LED will be off, and the orange LED will pulse continuously.
Above 1.55 the green LED will be off, and the red LED will pulse continuously.

SCR MODE

In SCR mode rEvodream assumes that sensors were calibrated with air at 1 bar ambient pressure. HUD ppO2 display changes - the 'green-only' zone is between 0.50 and 1.45.

The variations of PPO2 are symbolized as follows:

PO2 < 0,25 orange LED flashes rapidly
> 0,25 < 0,5 1 pulse of orange LED + green LED constantly on
> 0,5 < 1,45 green LED constantly on
> 1,45 < 1,55 1 pulse of red + green LED constantly on
> 1,55 red LED flashes rapidly

CHANGING MODES

All mode changes are made by specific number of piezo button presses when rEvodream is sitched on. After desired number of piezo button presses rEvodream turns on and green HUD LED flashes as many times as many times piezo button was pressed. Next, if mode change demands confirmation, you'll be asked for it (all 3 HUD LEDs flashes twice). Press piezo button once to confirm changes. rEvodream confirms saving new mode with rapid flashing of green LED and then turns off. 

4 presses (4P) - rEvodream is set to factory setting: HUD shows PPO2 according to the rEvo1.3 green zone pulsing, CCR mode. No confirmation is needed.

5 presses (5P) - rEvodream HUD will display the PPO2 using the rEvo 1.0 pulse code. Conformation is required.

6 presses (6P) - rEvodream HUD will display the PPO2 according to the SCR display mode. Conformation is required.