How to calibrate the *transmitter* with a *remote seal differential* which is implemented in *level* measurement.Actually, not like where I calibrate the detailed step by step (usually with a HART Communicator), which will be discussed in this *post* is how to determine the calibration parameters, so that *the transmitter* works on a range that we want according to the process conditions. But, prior to the calculation method determines the LRV and URV, let us recognize the term first.

There are two terms commonly used in the calibration of *the level transmitter* with *differential transmitter:*

**Zero Suppression**

*Zero suppressed* required if *the transmitter* pressure *gauge* or *absolute* installed under *tapping* the side of the high pressure (the bottom side of the process connection). If the *transmitter is* mounted below the *tapping* side of the high pressure, the liquid filler *(fill fluid)* in the capillary puts pressure on the sensor *transmitter* so as to provide a positive pressure reading even if the tank is empty.

**Zero Elevation**

Instead, *Elevated Zero* is required if the pressure *gauge* or *absolute transmitter* mounted above the high pressure tapping side (bottom side of the process connection) or on the application of the two*seal differential transmitter (low* side and *high* side). In this case, *the transmitter* reads a negative pressure when the tank is empty though. This is caused by the effect of *head pressure* on the fluid filler *(fill fluid)* on *the remote seal* capillary tube.

## 1. Suppressed Zero

Calibrating Transmitter System One Seal with suppressed Zero done if the transmitter is installed below the tapping point the high pressure side as shown below

From the picture above, it is known an open tank level is measured by a level transmitter that uses a single remote seal.

(s _{f)} = specific gravity of the fill fluid (liquid filler in the capillary of remote seal)

(h) = the distance between the process of tapping points to the transmitter.

(s _{p)} = specific gravity of process media that are in the tank.

(H) = The range of levels to be measured.

**step 1**

Calculate the amount of zero suppression by multiplying the distance between the process connection and the transmitter (h) by gravity liquid filler specifiec remote regret (s _{f):}

Zero Suppression = (h) (s _{f)} = (40 in) (0.93 INH _{2} O / in) = 37.2 INH _{2} O

**Step 2**

Calculate the span by multiplying the level range to be measured (H) by the specific gravity of the media that are in the process tanki.specific gravity (s _{p):}

Span = (H) (s _{p)} = (120 in) (1.2 INH _{2} O / in) = 144 INH _{2} O

**Step 3**

Determine / calculate calibration for the transmitter, which results in step 1 (zero suppression) as the LRV (Lower Range Value) and results in step 1 plus results in step 2 as the URV (Upper Range Value.

Calibration = “Zero Suppression” until (“Zero Suppression” + “Span”)

= 37.2 INH _{2} O to (37.2 + 144) INH _{2} O

INH _{2} O = 37.2 to 181.2 INH _{2} O

**Conclusion**

So, we calibrate the transmitter with:

LRV = 37.2 INH _{2} O

URV = 181.2 INH _{2} O

## 2. Elevated Zero – Open tank

Calibration is performed if the transmitter is mounted above (higher than) *the high side tap*

Is known:

**(s f) = 1.9 in H 2 O / inch**

**(h) = -30 inches**

**(s p) = 1.1 in H 2 O / inch**

**(H) = 120 inches**

From the picture above, it is known an open tank *level* measured her with a transmitter that uses a single *remote seal* with a transmitter is placed on the *high side tapping point.*

(s _{f)} = *specific gravity of the fill fluid* (liquid filler in the capillary of remote seal)

(h) = the distance between the *process of tapping points* to the transmitter (note the minus sign).

(s _{p)} = *specific gravity* of *process media* that are in the tank.

(H) = The range of *levels* to be measured.

**step 1**

Calculate the amount of *zero elevation* by multiplying the distance between the *process connection* and the transmitter (h) by the *specific gravity liquid* filler *remote regret* (s _{f):}

*Zero Suppression* = (h) (s _{f)} = (-30 in) (1.9 INH _{2} O / in) = -57 INH _{2} O

**Step 2**

Calculate the span by multiplying the *level* range to be measured (H) by the *specific gravity* of the *process media* are in the tank, *pecific gravity* (s _{p):}

Span = (H) (s _{p)} = (120 in) (1.1 INH _{2} O / in) = 132 INH _{2} O

**Step 3**

Determine / calculate *calibration* for the transmitter, which results in step 1 *(zero elevation)* as the LRV *(Lower Range Value)* and results in step 1 plus results in step 2 as the URV *(Upper Range Value).*

*Calibration* = *“Elevation Zero”* until *(“ZeroElevation”* + “Span”)

= -57 INH _{2} O to (-57 + 132) INH _{2} O

= -57 INH _{2} O to 75 INH _{2} O

**Conclusion**

So, we calibrate the transmitter with:

LRV = -57 INH _{2} O

URV = 75 INH _{2} O

## 3. Elevated Zero – Closed Tank

This calibration is done if a transmitter with *two seal* system installed one *tapping point levelÂ *with or above or below the *high pressure tap side.*

Is known:

**(Sf) = 1:07 in H2O / inch**

**(h) = – 400 inches**

**(Sp) = 0.9 in H2O / inch**

**(H) = 350 inches**

From the picture above, it is known an open tank *level* measured her with a transmitter that uses two *remote seals* each for *high* and *low pressure side* of his, the transmitter is placed under *the high side tapping point.*

(s _{f)} = *specific gravity of the fill fluid (liquid* filler in the capillary of *remote seal)*

(h) = the distance between the *process of tapping points* to the transmitter (note the minus sign).

(s _{p)} = *specific gravity* of *process media* that are in the tank.

(H) = The range of *levels* to be measured.

**step 1**

Calculate the amount of *zero elevation* by multiplying the distance between the *process connection* and the transmitter (h) by *gravity liquid* filler *specifiec remote regret* (s _{f):}

*Zero Elevation* = – (h) (s _{f)} = – (400 in) (1:07 INH _{2} O / in) = -428 INH _{2} O

**Step 2**

Calculate the *span* by multiplying the maximum height of the process fluid (H) by the *specific gravity* of the *process media* are in the tank, specific gravity (s _{p):}

Span = (H) (s _{p)} = (350 in) (0.9 INH _{2} O / in) = 315 INH _{2} O

**Step 3**

Determine / calculate *calibration* for the transmitter, which results in step 1 *(zero elevation)* as the LRV *(Lower Range Value)* and results in step 1 plus results in step 2 as the URV *(Upper Range Value).*

Calibration = *“Elevation Zero”* until *(“Elevation Zero”* + *“Span”)*

= -428 INH _{2} O until the (-428 + 315) INH _{2} O

= -428 To -113 INH INH _{2} O _{2} O

**Conclusion**

So, we calibrate the transmitter with:

LRV = -428 INH _{2} O

URV = -113 INH _{2} O

**Also Read: Importance of 4-20mA Current Loop**

## 17 comments

Thanks. I have no words for this superb website. How can I contact you Mr. Bharadwaj? Really awesome job.

Hello Akshay, You can contact me by mail at [email protected]

I am Instrument Engineer. Thanks

Thanks to everyone who involved in this website really sir it’s very owesome & very useful again I want to say many many thanks.

Amazing, can u explain that calibration methode suppresed zero is similar with steam drum level calibration?. Thanks

Hi, For Boiler Drum Level Calibration Click Here

I’m instrument technician.. This is very helpful… Thanks

Do you have a 3 element closed loop drawing for steam boiler instrumentation ?

For Boiler Three Element Control Please Click Here

Hi I’m female instrument technician. Really helpful info.. keep that good work sir..

Really good website this one ,how can i download this document

Hello, Please Open website in Desktop/PC and Click on Print Button available under the article heading to save in PDF. Thanks

dear sir

In above closed tank u have mentioned there as elevated zero,,,shouldnt be suppresed zero because transmitter is below hp side

second thing below (3) u mentioned

**From the picture above,it is known OPEN tank level…….. i think it should be closed instead of open

am i right?

Its really useful. What will be the formulas to calculate LRV and URV if it is direct flanged in HP and LP side is capillary connection.

Hi, Please check Level Measurement Category. Its available. Regards.

Thank you for the previous reply.. please explain why we include minus sign (-h) in “h” value for elevated zero-open and closed tank calculation.

REALLY THANKS A LOT TO THIS BHARDWAJ REDDY.BEACAUSE OF HIM SO MANY PEOPLE GAINING SO MUCH KNOWLEDGE ABOUT INSTRUMENTATION.