Change SI font in equation

Right now I have SI defined so:

\usepackage{siunitx}
\sisetup{
group-digits=integer,
group-minimum-digits = 4,
detect-display-math = true,
detect-weight,
detect-mode = true,
group-separator = {,}
}


My numbers are serif whereas I use Arial, which is a san serif font. Is it possible to make SI generate serif only when in equation mode?

sample equation:

\begin{subequations}
\label{eqn:decanterholdup}
\begin{align}
T & = 0.1\frac{\mu}{S_H - S_L} \\
& = 0.1 \frac{0.856551}{0.999492 - 0.88435} \nonumber\\
& = \SI{0.7439}{\hour}
\end{align}
\end{subequations}


text font:

\usepackage{helvet}


MWE:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{helvet}
\renewcommand{\familydefault}{\sfdefault}

\usepackage{siunitx}
\sisetup{
group-digits=integer,
group-minimum-digits = 4,
detect-display-math = true,
detect-weight,
detect-mode = true,
group-separator = {,}
}
\usepackage{amsmath}

\begin{document}

This is san serif. In the equation it is serif.

\begin{subequations}
\label{eqn:decanterholdup}
\begin{align}
T & = 0.1\frac{\mu}{S_H - S_L} \\
& = 0.1 \frac{0.856551}{0.999492 - 0.88435} \nonumber\\
& = \SI{0.7439}{\hour}
\end{align}
\end{subequations}

This text is san serif. \SI{5}{\cm}
\end{document}


The numbers in the math environment are serif fonts but the last line with SI is san serif. How can I make that last line in the math environment serif?

• Please provide an MWE, a complete small document beginning with \documentclass and ending with \end{document}. Mar 9 '20 at 18:04
• I'm afraid the sentence "My numbers are serif whereas I use Arial" makes no sense at all. Please clarify (a) what your document does at present and (b) what you would like it to do.
– Mico
Mar 9 '20 at 20:33
• I've added a MWE, please take a look again. Mar 9 '20 at 22:31
• The statement, "My numbers are serif" is still quite puzzling: It's not just the numbers, it's everything in math mode that's typeset using the (math) Roman font. Why do you appear to focus on the numerals? Please clarify.
– Mico
Mar 10 '20 at 20:25
• in \SI the numbers are san serif. I want to make them serif. Mar 10 '20 at 23:57