forum.heinrichsweikamp.com

Hi,

I am looking for a backup unit. I got several info on the ostc. Unfortunatly they aren't always the same. So I ran into trouble.

Some reports OSTC allow and calculate decompression profile for dive up to 120M. That's also what I can understand when I read ostc 2n description on this website heinrichsweikamp - ostc description - datasheet.

Other one report OSTC only allow calculated decompression profile for dive up 100M, but one can dive up to 120M in gauge mode (other even reports (ex deep-ideas - OSTC Description) a 140M gauge mode).

Other one reports OSTC crash when the unit read/detect 130M/14ATA. The only way to wake up the unit is to reset it when you are back at home, on the boat, at the hotel ...

A diver reports to me he got a calculted profile for a dive up to 126M. He reports me during the time he was diving > 120M - 126M, his OSTC always displayed a depth of 120M. Despite this false depth info, he got a correct decompression profile.

Is it possible to get reliable information on the actual max depth on which the OSTC 2N allows dives with calculated decompression profile.

Thanks for the help,

Frédéric

The pressure sensor in the OSTC is an INTERSEMA MS5541C
http://www.meas-spec.com/product/t_product.aspx?id=5035

Specs are:
• Integrated pressure sensor
• Pressure range 0 - 14 bar (200 PSI)
• Resolution 1.2 mbar
• Small size 6.2 x 6.4 mm
• 16 Bit ADC
• 6 coefficients for a software compensation stored on-chip
• 3-wire serial interface
• 1 system clock line (32.768 kHz)
• Temperature range -40..+85°C
• Low voltage (2.2 to 3.6V)
• Low power (Standby current: 0.1uA)
• Pb-free and RoHS-compatible
• No external components required

And yes the OSTC shuts down past 120m, its coded into the FW
Its all in this thread including a statment from HW:
http://forum.heinrichsweikamp.com/read.php?2,9026,9177#msg-9177

Hi Hansjoerg,

Thanks for your answer. Do I correctly understand it?

• The OSTC is able to calculate a decompression profile and so will help divers for dives up to 120m
• it is no documented how it works for dives > 120 and < 130m. One cann't say it will work in gauge mode or in deco mode
• When divers go deeper than 130m (14 ATA), the OSTC's firmware will crash. It is a heinrichsweikamp's design decision. It is definitively not a bug.

Thanks for the help.

Frédéric

You'll get a red depth reading (To show you that your warranty is void ) and somewhere between 130m and 140m (When the sensor is at the end of it's scale, they are individually calibrated so this varies) the unit will shut down intentionally.

Re-read the thread Hansjoerg referred to, where you can find the details.

Regards,
Matthias

Thx Matthias.

thanks

it is now clear for me.

Frédéric