[SS2S-Main] Re: temperature measurement
- From: "Nev Blyth" <nev.blyth@xxxxxxxxx>
- To: sugarshot@xxxxxxxxxxxxx
- Date: Tue, 25 Mar 2014 16:14:20 -0700 (PDT)
Cheers Ken - yes, your experiences are valuable indeed, and the Ublox certainly
has the support for these kind of high dynamics applications.
Will let you know what I learn in the future.
N
—
Nev Blyth
VK1HNB
0407 923 182
On Wed, Mar 26, 2014 at 10:06 AM, Ken Biba <ken@xxxxxxxxxxxxxx> wrote:
> Nev:
> Should do great for recovery location ... it is the trajectory location that
> separates the GPS chipsets IMO.
> Our flights are to 70-180k' MSL ... tickling Mach 3 ... so we are testing the
> limits of modern comercial GPS chipsets. So far the best has been uBlox.
> Altus Metrum used to use the MediaTek, but recently switched to uBlox.
> But this chipset does have "similar" specs - 515 m/s velocity, 40 km altitude
> ... I would be curious about the dynamics.
> I would have to dig out my old spreadsheets .. but there is such an obvious
> difference between a chipset that is prepared to deal with dynamics and one
> that is not. Most of my testing ahs been with SiRF, uBlox and Trimble
> chipsets. Getting lock is not sufficient .. .what is interesting is that
> reported location, under lock, is dramatically false for SiRF ... while
> largely accurate for uBlox and Trimble (when set to high dynamic mode) up to
> modest accelerations (<6-8 g).
> K
> Ken Biba
>> On Mar 25, 2014, at 3:54 PM, "Nev Blyth" <nev.blyth@xxxxxxxxx> wrote:
>>
>> Hi Ken
>>
>> (Apologies for getting OT here).
>>
>> I've only flown the MTK3339 based module three times - on H & I motors.
>> During those flights (3K ft only) I was not directly logging the NMEA stream
>> on board - rather I was using a simple telemetry system to stream the NMEA
>> to a recording ground station. Those flights showed valid data throughout,
>> but admittedly, the dynamics were rather benign in the scheme of things.
>> I'll have a look at the altimeter log for velocities.
>>
>> The axis of the GPS patch antenna was aligned normal to the vehicle's axis.
>> Admittedly, my main motivation was recovery location, not trajectory
>> recording, but I'll take what I get!
>>
>> Nev B
>> VK1HNB
>> —
>> Nev Blyth
>> VK1HNB
>> 0407 923 182
>>
>>
>>> On Wed, Mar 26, 2014 at 8:20 AM, Ken Biba <ken@xxxxxxxxxxxxxx> wrote:
>>> Nev:
>>>
>>>
>>> Now I'm curious. I fly the uBlox in large part because its signal
>>> processing seems to do really well for high dynamic flight (and while it
>>> has a spec limit of 50km, the factory says it will report above that
>>> altitude, though with diminished precision). It does stop reporting above
>>> the spec limit of ~515m/s ... though does resume reporting when the speed
>>> drops below that.
>>>
>>> Many GPS chipsets perform poorly in high dynamic rocket flight ... since
>>> the signal processing is biased to solve the 2D problem with high precision
>>> rather than the fast changing 3D problem. The uBlox has a specific
>>> configuration parameter to set the movement model ... I don't see that on
>>> the MediaTek manual.
>>>
>>> Do you configure in default mode?
>>>
>>> Ken
>>>
>>>
>>>
>>>> On Mar 25, 2014, at 2:08 PM, Nev Blyth <nev.blyth@xxxxxxxxx> wrote:
>>>>
>>>> Nathan - the adafruit GPS module is excellent - has flown multiple times
>>>> in my high-power rockets and maintained a solid lock throughout the whole
>>>> flight. If I recall, the module is programmable, has PPS output and the
>>>> price is excellent. Would be interesting to compare against the ublox
>>>> offerings. The external antenna connection is a bonus for me.
>>>>
>>>> Cheers,
>>>>
>>>> Nev. B
>>>>
>>>> ___________________
>>>> Nev. Blyth, VK1HNB
>>>> Canberra, ACT, Australia
>>>> @nevblyth
>>>> facebook.com/nevblyth
>>>>
>>>>
>>>>> On 26 March 2014 05:40, Nathan Asdourian <rawliquid@xxxxxxxxx> wrote:
>>>>> you would be much better off with a ublox that is fully configurable and
>>>>> reprogrammable, not to mention the latest version has a compass module
>>>>> in it.... i think it's more than $40 though it is the unit from
>>>>> 3drobotics.com and what i use in my helis
>>>>>
>>>>>> On Mar 25, 2014 10:47 AM, "Rick Maschek" <rickmaschek@xxxxxxxxxxxxxx>
>>>>>> wrote:
>>>>>> Hi Nathan,
>>>>>>
>>>>>> and this may be going up on our next Near Space balloon launch:
>>>>>>
>>>>>> http://www.adafruit.com/products/746
>>>>>>
>>>>>> Are bitcoins worth anything anymore?
>>>>>>
>>>>>> Rick
>>>>>>
>>>>>>
>>>>>> On Tuesday, March 25, 2014 6:37 AM, Nathan Asdourian
>>>>>> <rawliquid@xxxxxxxxx> wrote:
>>>>>> Please forgive me if these items are irrelevant due to the extremes
>>>>>> needing to be dealt with but I just saw a new board get released here a
>>>>>> few weeks ago, and all the related things seem to be under $20
>>>>>> http://www.adafruit.com/index.php?main_page=adasearch&q=thermocouple
>>>>>> And of course if anyone has some bitcoin stashed away, they will accept
>>>>>> that for payment...
>>>>>> On Mar 24, 2014 9:20 PM, "Lampe, Mattias SLC CT PEK"
>>>>>> <mattias.lampe@xxxxxxxxxxx> wrote:
>>>>>> Hi Richard,
>>>>>>
>>>>>> my personal choice would probably be to use an integrated chip that does
>>>>>> everything, including D/A-conversion, e.g. the MAX6675:
>>>>>>
>>>>>> http://item.taobao.com/item.htm?spm=a230r.1.14.48.TLryFm&id=13831142184
>>>>>>
>>>>>> Since it may be more convenient for you to use the existing DAC, you may
>>>>>> prefer one of the older chips with analog output, though. AD595 would be
>>>>>> a good choice:
>>>>>>
>>>>>> https://www.sparkfun.com/products/306
>>>>>>
>>>>>> Of course you'll need to have a loot at the datasheets to see whether
>>>>>> the devices match the temperature range you need.
>>>>>>
>>>>>> Hope it helps.
>>>>>>
>>>>>>
>>>>>> Have a good day!
>>>>>>
>>>>>> Mattias
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> >-----Original Message-----
>>>>>> >From: sugarshot-bounce@xxxxxxxxxxxxx [mailto:sugarshot-
>>>>>> >bounce@xxxxxxxxxxxxx] On Behalf Of Richard Nakka
>>>>>> >Sent: Monday, March 24, 2014 10:33 PM
>>>>>> >To: sugarshot@xxxxxxxxxxxxx
>>>>>> >Subject: [SS2S-Main] temperature measurement
>>>>>> >
>>>>>> >For an upcoming motor test, we would like to use thermocouples
>>>>>> >(k-type?) to measure motor casing and nozzle temperatures.
>>>>>> >We would like to use an 8-channel DATAQ unit for the data acquisition.
>>>>>> >
>>>>>> >We understand there are challenges to this due to small voltage
>>>>>> >signal, non-linear temperature-voltage relationship and the need (?)
>>>>>> >for a reference junction compensation.
>>>>>> >
>>>>>> >Question to list members: Can anyone give advice on how to do this?
>>>>>> >What kind of amp would we need? Could anyone be of assistance in
>>>>>> >designing/building such?
>>>>>> >
>>>>>> >
>>>>>> >thanks in advance
>>>>>> >Richard
>>
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