We generated total revenue growth of 13.6% and core revenue growth of 9.1%, above the high-end of our guidance.
Adjusted earnings per share was $0.63, representing an increase of 37% year-over-year.
In 2020, we more than doubled the number of projects conducted and expect to do the same this year, targeting more than $250 million of potential revenue opportunity.
In terms of performance across the major geographies, core growth was led by low 20% growth in Asia.
This included approximately 30% growth in China and low double-digit growth in Japan.
Taking a closer look at performance in the segments on slide seven, Intelligent Operating Solutions posted a total revenue increase of 9.5%, with core revenue increase of 5.5%.
Fluke's growth included the launch of the 377 and 378 Fluke Connect, plant meters for non-contact voltage testing.
iNet also registered an 18% increase in bookings, while driving a more than 500 basis point improvement in net retention.
The Precision Technology segment posted a total revenue increase of 14.3% with a 12.1% increase in core revenue.
Point-of-sale continue to accelerate, up greater than 40% in China, greater than 20% in Western Europe, while North America turned positive with a mid single-digit increase in the quarter.
Mainstream oscilloscope posted high 30% growth, driven by strong demand trends across most of its key product segments, particularly our six series and four series scopes.
Sensing also generated strong growth from its critical environment products, etc, with mid-30% growth for the quarter.
The business continued to see good order trends with a book-to-bill of 1.2 over the trailing 12 months and has a strong backlog that we expect to support improving growth in the coming quarters.
Total revenue increased 20.3% with a 10.9% increase in core revenue.
This included low 40% growth in China, low 20% growth in Western Europe and low single-digit growth in North America.
Growth at ASP was driven by a greater than 40% increase in capital equipment sales as it continued to grow its global installed base.
This momentum in capital sales more than offset the fact that electric procedures were 91% of pre-COVID levels globally and continue to weigh on ASP's consumable revenue.
Landauer is now seeing an approximate 2.5 times improvement in its operating margins since acquisition.
Finally, Invetech reported mid-40% growth as it delivers against a strong backlog of 2020 orders for its diagnostic offerings.
Adjusted gross margins were 57% in the first quarter, up 90 basis points, driven by the fall-through on the strong growth at Fluke and Tektronix as well as the year-over-year gross margin improvement at ASP coming off the transition service agreements.
It also reflected solid execution with FBS throughout the portfolio, including continued price realization of 90 basis points in the quarter.
Our Q1 adjusted operating profit margin was 22.7%, a bit higher than we had guided, helped in part by the stronger volume we saw in the quarter.
We generated 40% of adjusted incremental operating margins and 240 basis points of core operating margin expansion and also generated more than 200 basis points of core operating margin expansion in each of our three segments.
During the first quarter, we generated $144 million of free cash flow, representing an increase of 50% year-over-year.
We continue to be pleased with the consistent growth in free cash flow and have delivered -- that we've delivered over the past year, with the first quarter taking our trailing 12 months free cash flow to $950 million.
Early in Q1, we executed the tax-efficient monetization of our remaining 19.9% stake in Vontier, generating approximately $1.1 billion in proceeds which we used for debt repayment.
On the basis of that transaction and our free cash flow from Q1, we ended up the first quarter with a net leverage ratio of 1.2 times.
For the full year, we now expect adjusted diluted net earnings per share to be $2.50 to $2.60, representing year-over-year growth of 20% to 24% on a continuing operations basis.
This assumes total revenue growth of 10% to 13%, core revenue growth of 7% to 10%, adjusted operating profit margins of 22% to 23% and an effective tax rate of approximately 14%.
It also assumes core revenue growth of 5% to 7% in the second half of 2021.
We also continue to expect free cash flow conversion to be approximately 105% of adjusted net income for the year.
We are initiating second quarter adjusted diluted net earnings per share guidance of $0.56 to $0.60, representing year-over-year growth of 30% to 40%.
This assumes total revenue growth of 20% to 23%, core revenue growth of 16% to 19%, adjusted operating profit margins of 19.5% to 20.5% and an effective tax rate of approximately 14%.
For the second quarter, we expect free cash flow conversion to be approximately 85% of adjusted net income.
The full year guidance incorporates $35 million of additional investments that we are making to drive innovation and enhance our capabilities to support higher growth in the years ahead with $15 million in the second quarter.

Summary:
We generated total revenue growth of 13.6% and core revenue growth of 9.1%, above the high-end of our guidance.
Adjusted earnings per share was $0.63, representing an increase of 37% year-over-year.
For the full year, we now expect adjusted diluted net earnings per share to be $2.50 to $2.60, representing year-over-year growth of 20% to 24% on a continuing operations basis.
We are initiating second quarter adjusted diluted net earnings per share guidance of $0.56 to $0.60, representing year-over-year growth of 30% to 40%.