Message-ID:

Systems programmers are the high priests of a low cult. -- R. S. Barton

tech / sci.electronics.design / about isolator for PH probe

about isolator for PH probe

<47eb8c27-1719-4a0e-b0e0-53af332e693an@googlegroups.com>

https://www.novabbs.com/tech/article-flat.php?id=102813&group=sci.electronics.design#102813

copy link Newsgroups: sci.electronics.design

X-Received: by 2002:a05:620a:2844:b0:6b8:5f52:a6b5 with SMTP id h4-20020a05620a284400b006b85f52a6b5mr10384665qkp.351.1659329746468;
Sun, 31 Jul 2022 21:55:46 -0700 (PDT)
X-Received: by 2002:a25:e7c2:0:b0:673:83d4:ce03 with SMTP id
e185-20020a25e7c2000000b0067383d4ce03mr9333199ybh.381.1659329746224; Sun, 31
Jul 2022 21:55:46 -0700 (PDT)
Path: i2pn2.org!i2pn.org!usenet.blueworldhosting.com!feed1.usenet.blueworldhosting.com!peer03.iad!feed-me.highwinds-media.com!news.highwinds-media.com!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: sci.electronics.design
Date: Sun, 31 Jul 2022 21:55:46 -0700 (PDT)
Injection-Info: google-groups.googlegroups.com; posting-host=103.136.92.114; posting-account=fnj1vAoAAAAVcpDGWhwT5Qq42JJb193e
NNTP-Posting-Host: 103.136.92.114
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <47eb8c27-1719-4a0e-b0e0-53af332e693an@googlegroups.com>
Subject: about isolator for PH probe
From: piyushka...@gmail.com (Piyush Kamdi)
Injection-Date: Mon, 01 Aug 2022 04:55:46 +0000
Content-Type: text/plain; charset="UTF-8"
X-Received-Bytes: 1138

by: Piyush Kamdi - Mon, 1 Aug 2022 04:55 UTC

i use the analog isolator from atlast scintific but it is quiet expensive so suggest me the cheap isolator circuit in india . (for ph probe )

Re: about isolator for PH probe

<ced600af-4340-4e1d-acc7-3ea04caa913fn@googlegroups.com>

copy mid

https://www.novabbs.com/tech/article-flat.php?id=102816&group=sci.electronics.design#102816

copy link Newsgroups: sci.electronics.design

X-Received: by 2002:a05:622a:488:b0:31e:f6e8:6ec4 with SMTP id p8-20020a05622a048800b0031ef6e86ec4mr12706086qtx.351.1659335122548;
Sun, 31 Jul 2022 23:25:22 -0700 (PDT)
X-Received: by 2002:a0d:d9c7:0:b0:324:6979:1606 with SMTP id
b190-20020a0dd9c7000000b0032469791606mr8654662ywe.69.1659335122317; Sun, 31
Jul 2022 23:25:22 -0700 (PDT)
Path: i2pn2.org!i2pn.org!usenet.blueworldhosting.com!feed1.usenet.blueworldhosting.com!peer03.iad!feed-me.highwinds-media.com!news.highwinds-media.com!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail
Newsgroups: sci.electronics.design
Date: Sun, 31 Jul 2022 23:25:22 -0700 (PDT)
In-Reply-To: <47eb8c27-1719-4a0e-b0e0-53af332e693an@googlegroups.com>
Injection-Info: google-groups.googlegroups.com; posting-host=63.114.57.174; posting-account=I-_H_woAAAA9zzro6crtEpUAyIvzd19b
NNTP-Posting-Host: 63.114.57.174
References: <47eb8c27-1719-4a0e-b0e0-53af332e693an@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <ced600af-4340-4e1d-acc7-3ea04caa913fn@googlegroups.com>
Subject: Re: about isolator for PH probe
From: gnuarm.d...@gmail.com (Ricky)
Injection-Date: Mon, 01 Aug 2022 06:25:22 +0000
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Received-Bytes: 1899

by: Ricky - Mon, 1 Aug 2022 06:25 UTC

On Monday, August 1, 2022 at 12:55:48 AM UTC-4, Piyush Kamdi wrote:
> i use the analog isolator from atlast scintific but it is quiet expensive so suggest me the cheap isolator circuit in india . (for ph probe )

By "isolator", I assume you mean a high input impedance amplifier? I know pH probe have a very high impedance, so nearly any current draw will create an error. I don't know how high the impedance needs to be. This may require a circuit with a bootstrap and guard rings. Do you have a schematic? Perhaps you can make your own. Have you looked for sample circuits?

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

Re: about isolator for PH probe

<tc87t2$1s6g$1@gioia.aioe.org>

copy mid

https://www.novabbs.com/tech/article-flat.php?id=102822&group=sci.electronics.design#102822

copy link Newsgroups: sci.electronics.design

Path: i2pn2.org!i2pn.org!aioe.org!U54xAdP7pvGKboowhQIuJQ.user.46.165.242.75.POSTED!not-for-mail
From: '''newsp...@nonad.co.uk (Martin Brown)
Newsgroups: sci.electronics.design
Subject: Re: about isolator for PH probe
Date: Mon, 1 Aug 2022 10:54:41 +0100
Organization: Aioe.org NNTP Server
Message-ID: <tc87t2$1s6g$1@gioia.aioe.org>
References: <47eb8c27-1719-4a0e-b0e0-53af332e693an@googlegroups.com>
<ced600af-4340-4e1d-acc7-3ea04caa913fn@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Info: gioia.aioe.org; logging-data="61648"; posting-host="U54xAdP7pvGKboowhQIuJQ.user.gioia.aioe.org"; mail-complaints-to="abuse@aioe.org";
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:91.0) Gecko/20100101
Thunderbird/91.11.0
Content-Language: en-GB
X-Notice: Filtered by postfilter v. 0.9.2

by: Martin Brown - Mon, 1 Aug 2022 09:54 UTC

On 01/08/2022 07:25, Ricky wrote:
> On Monday, August 1, 2022 at 12:55:48 AM UTC-4, Piyush Kamdi wrote:
>> i use the analog isolator from atlast scintific but it is quiet
>> expensive so suggest me the cheap isolator circuit in india . (for
>> ph probe )

Their OEM pH board doesn't look unreasonably priced to me:

https://atlas-scientific.com/embedded-solutions/ph-oem-circuit/

> By "isolator", I assume you mean a high input impedance amplifier? I
> know pH probe have a very high impedance, so nearly any current draw
> will create an error. I don't know how high the impedance needs to
> be. This may require a circuit with a bootstrap and guard rings.

A working approximation is around 1G worst case.

You would probably get away without a guard band provided that the
humidity and ambient temperature isn't too high. Many opamps the input
bias current rises quickly with temperature above 25C ambient.

> Do you have a schematic? Perhaps you can make your own. Have you
> looked for sample circuits?

If you don't care too much about thermal drift or precision calibration
then almost any modern FET input opamp will be adequate in a unity gain
voltage follower configuration. eg #9.3 in TL071 datasheet

https://www.ti.com/lit/ds/symlink/tl071.pdf

Or a more recent automotive part like

https://www.ti.com/lit/ds/symlink/ina333-q1.pdf

If you do care about precision calibration and have to ask this question
then you are probably much better off with a commercial product.

--
Regards,
Martin Brown

Subject	Author
about isolator for PH probe	Piyush Kamdi
Re: about isolator for PH probe	Ricky
Re: about isolator for PH probe	Martin Brown