Can i use this in the sump of my aquarium rack, by just mounting the sensors in the water in the sump? ie not inline in an ro/hma system?

There are 2 problems. The sensors are calibrated to be used as advised and in open water they will give much higher readings as well as having the uncertainty of their durability. The latter issue is not a short term problem as they are just 2 probes on the end of a pair of wires. It all depends on what you want to achieve.

Tds meter should 2 digit result. should this be 3 digit? e.g 000ppm ??

Its a 3 digit readout on an instrument with 2% accuracy. Do not confuse accuracy and precision. Accuracy is how close to the correct result is it? 2% is 2 parts in 100, so some of second digit and all the third digit are wasted. It can determine only 50 TDS steps. Precision is what does it display? The display has 1000 steps, so its very precise. That is 0.1% precision.

I have an RO unit with a post filter to reinstate minerals, should this be installed before the post filter? Or will readings be affected?

I have mine after the water comes out of to unit I think if you put post filter all minerals could be filtered out

Trying to recalibrate while disconnected from RO unit but the in and out probes give different readings, why?

The probes have to be in the pipe to read. They will not give a “correct” reading if pulled out of and say placed in a cup. You would need to use the T connectors and loop a piece of pipe around

Fully operational. Shipping worldwide, on schedule.Duty & taxes paid at delivery

Help Track order

Account Cart

Fully operational. Shipping worldwide, on schedule.Duty & taxes paid at delivery

Help Track order

Account Cart

HM Digital DM-1 in-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy

HM Digital DM-1 in-Line Dual TDS Monitor, 0-9990 ppm Range, +/- 2% Readout Accuracy

Product ID: 48028052

Details

Brand
HM Digital
Item dimensions L x W x H
48 x 20 x 76
Item weight
0.1 Pounds
Material
Plastic
Number of items
1

💧0-9990 ppm TDS range

🔋Auto-off power saving

⚙️+/- 2% readout accuracy

239.78 DT

Duties & taxes included

In stock

Sold byAmazon TunisiaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Tunisia.

Secure transaction

Description

💧 Stay ahead of purity—know your water’s story in real time!

DUAL SENSOR PRECISION - Simultaneously monitor feed and purified water TDS for real-time filtration performance insights.
SMART POWER MANAGEMENT - Auto-off feature conserves battery life, so your monitor is ready when you need it.
EFFORTLESS INSTALLATION - Quick-connect T-fittings and compact design make setup seamless—get monitoring in minutes.
ULTRA WIDE DETECTION RANGE - Measures TDS from 0 to 9990 ppm, covering everything from tap water to highly purified sources.
MICROPROCESSOR DRIVEN ACCURACY - Advanced tech ensures readings within ±2%, empowering confident water quality decisions.

The HM Digital DM-1 is a compact, dual in-line TDS monitor designed for professional-grade water filtration systems. It measures total dissolved solids from 0 to 9990 ppm with ±2% accuracy using two electrode probes to track both incoming tap water and purified output. Featuring advanced microprocessor technology, quick installation with included fittings, and an auto-off function to save battery, it’s the essential tool for ensuring optimal filter performance and water purity.

Specifications

ASIN	B001EHAZGW
Best Sellers Rank	10,225 in Business, Industry & Science ( See Top 100 in Business, Industry & Science ) 45 in Liquid Analysis Instrumentation 110 in Lab Meters
Brand	HM Digital
Country Of Origin	China
Customer Reviews	4.7 4.7 out of 5 stars (2,701)
Global Trade Identification Number	00891144000052
Included Components	Bag
Item Dimensions	48 x 20 x 76 millimetres
Item Weight	0.1 Pounds
Manufacturer	HM Digital, Inc.
Manufacturer Part Number	DM-1
Material	Plastic
Model Number	716186
Number of Items	1
Set Name	Dual
UPC	733169337600 891144000052 885169394012 885156810310
Unit Count	1.0 count

Common Questions

Are the products genuine and authentic?+

Yes, all products are sourced directly from authorized retailers in the US, UK, UAE and India. We maintain strict quality control processes and verify each product before shipping. All items come with applicable manufacturer warranties and are covered by our standard return policy.

How long does delivery take and is it reliable?+

Delivery times vary by destination country, typically ranging from 3-9 business days. Each order is fully trackable through our system. We handle all customs clearance and use reliable courier partners for last-mile delivery. You'll receive regular updates about your order status via email and our app.

What is Desertcart? Is it safe to order from?+

Desertcart is an international e-commerce platform operating since 2014. We securely process thousands of orders globally each day. Every product goes through our quality verification process before delivery, and we provide end-to-end order tracking, 24/7 customer support, and a comprehensive returns policy to ensure a safe shopping experience.

How is product pricing calculated?+

Our prices include the product cost, international shipping, import duties, customs clearance, and local delivery charges. We handle all customs and import procedures, ensuring there are no hidden fees upon delivery. PRO members receive additional benefits including free shipping.

Trustpilot

TrustScore 4.5 | 7,300+ reviews

Ayesha M.

The product exactly matches the description. Very satisfied with my purchase.

5 days ago

Farhan Q.

The delivery time was excellent, and the packaging was secure.

2 months ago

View all Trustpilot reviews

Shop Global, Save with Desertcart

Value for Money

Competitive prices on a vast range of products

Shop Globally

Serving millions of shoppers across more than 100 countries

Enhanced Protection

Trusted payment options loved by worldwide shoppers

Customer Assurance

Trusted payment options loved by worldwide shoppers.

Desertcart App

Shop on the go, anytime, anywhere.

239.78 DT

Duties & taxes included

In stock

Sold byAmazon TunisiaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Tunisia.

Secure transaction

Trustpilot

TrustScore 4.5 | 7,300+ reviews

Rajesh P.

Customer service was outstanding when I had questions about the product.

2 days ago

Meera L.

Smooth transaction and product arrived in perfect condition.

3 weeks ago

View all Trustpilot reviews